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Comprehensive Error-Variety Checklist

Compiled by Mike Diamond

This checklist is my attempt to compile a comprehensive listing of all known variety and error types, subtypes, and associated effects. It is updated periodically to reflect the current state of knowledge.

While the traditional planchet-die-striking method of classification hasn’t been completely abandoned, it has been absorbed into a much more detailed and precise taxonomy. This is intended to reflect the numerous steps (and missteps) in the minting process that generate the great diversity of anomalies presented here.

Many of the categories will be familiar to veteran collectors. Others will perhaps be dimly recalled, while others will be unfamiliar. Many of the more obscure error types have been treated in detail in articles published in Errorscope. These articles are referenced next to the appropriate entry (“ES”). Other treatments can be found in Coin World (“CW”).

I have tried to restrict this checklist to basic error/variety types and subtypes. Combination errors have been kept to a minimum. Had I attempted to incorporate all conceivable two-error combinations, this would have generated almost half a million entries. That would have been both unwieldy and unnecessary.

ES=Errorscope

CW=Coin World

Part I. Die Subtypes:

Patterns and Prototypes (accidental release)

Mid-year design modifications

Conceptual design flaws (foul-up in design or in translating design to master hub or master die) (CW 11/15/21)

 Mistakes during design modification

    • 2007 Mexico 10 pesos with reversed dentils
    • 2008 Chile 50 pesos with country spelled “CHIIE”

Unauthorized strikes and unauthorized issues (CW 1/20/14)

    • 1913 Liberty Head nickel
    • 1954 Mexico 5 centavos (small size)

Part II. Die Varieties:

Reduction lathe doubling (master hub doubling)

Master die doubling (master die with a doubled die variety) (CW 7/27/20)

Broken hub (chipped hub) (CW 12/23/13, 5/21/18)

Hubbed-in debris (CW 5/27/13, 1/17/22)

Broken punch

Damaged punch

Defective punch

Longacre doubling (probably impressions of punch shoulders)

Doubled dies (incl. tripled dies, etc)

Weak or incomplete hubbing (always part of a doubled die)

Tilted hubbing (always part of a doubled die)

Misaligned hubbing (uncorrected) (CW 5/30/22)

Repunched dates (ES July/August 2012; CW 12/14/09)

Re-engraved dates (on master die or working die)

Blundered dates (on master die or working die)

Misplaced dates (e.g. digits in denticles) (CW 4/21/03)

Misplaced mintmarks

Phantom mintmarks (working hub has mintmark incompletely removed)

    • (e.g. faint D and S mintmarks in cents from the late 1990s)

Dual mintmarks

    • 1980 D & S cent (recently delisted)
    • 1956 D & S cent (controversial)

Horizontal mintmarks (inevitably repunched)

Tilted mintmarks (punched in at an angle) (CW 7/28/14)

Rotated mintmarks (CW 7/28/14)

Inverted mintmarks

Deeply-punched (high-standing) mintmarks (CW 9/29/14)

    • High-standing D mintmark (1987-D, 1988-D, and 1989-D cents)

Weakly-punched mintmarks

Repunched mintmarks (CW 1/20/20)

Repunched mintmarks on the Jefferson nickel; Book by James Wiles (downloadable version)

Overmintmarks

    • 1938-D/S Buffalo Nickel
    • 1944-D/S cent

Other repunched or re-engraved design elements

Omitted mintmarks

    • 1982 “no-P” Roosevelt dime
    • 1990 Lincoln proof cent without S-mintmark

COIN WORLD SPECIAL: article posted HERE  on 1975-S Roosevelt dime without mintmark

Omitted dates (foreign only) (CW 4/28/14)

Other omitted design elements

Large over small mintmarks

Different mintmark styles and sizes

Overdates (CW 1/23/17)

Dual Dates (earlier date faint)

    • Caused by erasing earlier date on working hub
    • Caused by removing earlier date from working die and re-hubbing (e.g. 1975 Bahamas 5c with faint date “1973” on opposite face)

Wrong dates

    • Date later than final date of issue (e.g., 1913 Liberty Head nickel)
    • Date earlier than first date of issue (e.g., 1954 Mexico 5 centavos – small size)
    • Wrong digits (e.g., 1393/1893 Peruvian peso)
    • Transposed digits

Blundered dies (various types) (CW 8/18/08)

Special Finish Errors (Proofs, Mint sets, Special Mint Sets, Satin Finish, etc.)

Design Extension Dimples (CW 4/18/11) 

    • COIN WORLD SPECIAL: article posted HERE

Edge Lettering Font Variants 

    • Presidential dollars (4-5 types) (CW 10/18/10)

Hidden Initials And Symbols 

    • Applied to working die or master die
      • 1973 and 1974 Mexico Bronze 20 Centavos
      • 1984 Mexico 1 Peso
    • Applied to working hub
      • 2023 “extra V” cent (CW 3/27/23)

Part III. Die Installation Errors:

 Mules (ES May/June 2010)

    • Wrong hammer die
      • 2005 Malaysian 1 sen obverse die paired with 10 sen reverse die and struck on a copper-nickel 10 sen planchet in a 10 sen collar
      • 1995 cent/dime mule
    • Wrong anvil die
      • Malaysian 1 sen reverse die paired with a 2005 10 sen obverse die and struck on a copper-nickel 10 sen planchet in a 10 sen collar
      • 1993-D and 1999 cent/dime mules
    • Wrong hammer and anvil die
      • 2005 Malaysian 1 sen obverse and reverse dies used to strike a 10 sen planchet in a 10 sen collar
      • Maryland quarter on Sac planchet in Sac collar (3 specimens)
    • Two anvil dies
      • Foreign
        • 1982 Jamaica cent with two obverse faces
        • Chilean 100 pesos bi-metallic with two obverse faces (1 known specimen)
        • 1 Euro cent with two reverse faces
      • Domestic
        • Two-tailed clad dime (1 known specimen, probably from 1965)
        • Two-tailed clad quarter (3-4 known specimens, probably from 1965)
    • Two hammer dies
      • Foreign
        • 1982 Jamaica cent with two reverse faces
      • Domestic
        • 1859 Indian cent with two obverse faces (unique)
        • 1863 Broas Pie Bakers token (Civil War Store card token)
    • Two obverse or two reverse dies (die setup unclear)
      • 2000-P nickel with two obverse dies (CW 6/26/17)
    • Two different countries
      • (1967) Bahamas 5c/New Zealand 2c mule
    • Different denominations
      • Washington 25c/Sacagawea $1 mules (16 specimens, 3 die pairs)
        • COIN WORLD SPECIAL: article posted HERE
    • Mule die larger than normal die and collar
      • 1995 cent/dime mule
    • Mule die same size or smaller than normal dies and collar
      • (All known U.S. mules employ dies of different sizes)
    • Temporal mule (mule die representing same denomination but from an earlier or subsequent year) (CW 1/24/14)
    • Temporal/transitional mule (dies from different years with change in planchet composition) (CW 5/9/16)
    • Regular-issue die muled with commemorative die
    • Regular-issue die muled with government medal or token die
    • Regular-issue die muled with private token, medal, or nonsense die (ES Jan/Feb 2008; CW 11/25/13)
    • Mules involving pattern dies  (various types)
      • Normal die paired with pattern or prototype die (CW 2/2/04)
    • Collar mules  (collar from different denomination of same or similar size installed)
    • Lettering die mule (mismatch between edge lettering applied before or after strike and the design shown on the obverse and reverse face)
      • Presidential dollar with wrong date on edge.
        • 2009 Zachary Taylor dollar with 2010-D edge inscription (rather than 2009-D inscription) (CW 2/22/10, 3/1/10)
      • 2007-D Sacagawea dollar with Presidential dollar edge lettering (CW 7/9/12)
    • Pseudo-mules  (3 pathways)
      (CW 4/25/11, 3/19/12, 4/23/12, 12/11/17, 12/17/18, 2/22/21, 12/12/22, 1/15/24)
      COIN WORLD SPECIAL: article posted HERE

      • Canadian Pseudo-mules     
        • COIN WORLD SPECIALS: articles posted HERE  and HERE
      • One U.S. two-tailed quarter may belong in this group (CW 11/27/04, 8/27/12)

Mismatched business / proof dies

Finished proof die matched with business die

    • Early 19th century examples (CW 8/20/12)

Transitional Reverse (Minor temporal mismatches) e.g.:

Inverted die installation (not an error) (CW 2/15/10, 7/22/19, 1/6/20)

    • Older issues struck with inverted dies (e.g. buffalo nickels and Mercury dimes)
    • Re-introduction of inverted dies (beginning 1989) (CW 12/4/23, 12/11/23)
    • Saddle strikes produced by inverted dies (CW 9/13/10, 9/19/16)

Late use of traditional die setup (CW 6/5/18)

Fixed rotated die errors (see Part VI)

Collar installation errors

    • Smooth edge instead of reeded edge (and vice versa)
      • 1863 Indian cent with reeded edge (CW 6/3/02)
    • Smooth edge instead of edge design (and vice versa)
    • Reeded edge instead of edge design (and vice versa)
    • Segmented proof collar with segments out-of-order (CW 4/7/08)
      • 2007-S Proof Presidential dollar with segments arranged in wrong sequence (CW 4/7/08)

Use of flat, featureless dies   (CW 6/30/14)

Use of cancelled and defaced dies  (CW 5/12/14)

Cancelation overstrikes (coins overstruck by canceled coin, pattern, or test dies) (CW 5/18/17, 5/24/21)

Design/composition mismatches (CW 2/10/20)

Part IV. Die Errors:

Reeding vs. no reeding varieties (foreign only)

Concentric lathe lines  (ES Nov/Dec 2003)

    • Various years and denominations
      • Common on the 1996-D Lincoln cent

Rusted dies   (CW 12/1/08)

Excessively deep rim gutter

    • 1991 cents

Rockwell test mark left in die  (hemispherical bump seen on coin) (ES July/Aug 2006)

Vickers test mark left in die  (pyramidal bump) (CW 5/15/17)

Collar manufacturing errors

    • Wide collar  (ES Nov/Dec 2002; CW 5/17/10)
      • Created by improper machining or improperly machined broach
      • Created by use of wrong broach
      • Improper use of correct broach
      • Widening due to wear
      • Widening due to 3 or more vertical collar cracks and associated expansion (CW 5/17/10)
    • Abnormal reeding
      • 1921 Morgan dollar with infrequent reeding
      •  1924-D Mercury dime with infrequent reeding
      • 2015 American Eagle 1/10 oz. gold bullion coin with narrow reeds (CW 7/13/15)
      • Low, narrow reeds caused by truncation of ridges on collar face  (ES March/April 2010; CW 1/25/10, 4/16/12) 
        • 1964-D 25c
        • 2008-P New Mexico 25c
          • COIN WORLD SPECIAL: article posted HERE

Hub retouching

Die retouching (CW 5/30/16, 9/30/19)

Die damage (ES Jan/Feb 2003, Nov/Dec 2004; CW 5/21/12)

    • Die dents
      (ES Nov/Dec 2004, July/August 2005, Nov/Dec 2005; CW 9/15/03, 12/22/14, 3/28/22, 7/31/23)
    • Die scrapes  (CW 4/23/07)
    • Accidental die scratches
    • Die gouges
    • Impact scars
    • Accidental die abrasion  (CW 9/8/14, 12/16/19)
    • Intentional die abrasion (“die polishing”) (CW 3/29/10, 5/31/10, 9/8/14, 3/20/23)
    • Defects related to die polishing
      • Over-polished proof and Special Mint Set dies (CW 2/21/11)
      • Trails and Wavy Steps (ES July/Aug 2006, Sept/Oct 2006, Nov/Dec 2006, Jan/Feb 2011; CW 3/8/10)
      • Localized removal of field from proof polishing  (CW 2/14/11)  
        • COIN WORLD SPECIAL: article posted  HERE
    • Die attrition errors  (ES May/June 2003, March/April 2005, March/April 2009; CW 1/4/10, 12/24/12, 4/14/14, 11/4/19, 7/3/23, 10/16/23)
    • Other forms of peripheral die damage  (ES March/April 2005; CW 8/9/21, 3/14/22)
    • Catastrophic die damage  (ES March/April 2002; CW 9/15/03, 9/12/11, 9/19/11, 5/20/13, 10/27/14, 6/19/17)
    • Cancelled or defaced dies (foreign only) (CW 5/8/17, 12/31/18)
      • 1994 Hong Kong bimetallic 10 dollars
      • Egypt 25 piastres struck by defaced 50 piastres dies (CW 5/12/14)
      • 1966 Bolivia 10 centavos struck by pair of canceled dies (CW 5/8/17)
      • Chilean test dies with concentric cancellation pattern struck over struck foreign core (CW 5/8/17)
    • Rockwell test mark in die (CW 5/15/17)
    • Vickers test mark in die (CW 5/15/17)
    • Die rings (tiny rings, semicircles, crescents, and spirals)  (CW 2/20/17, 1/18/21, 6/13/22)
        • Centrally-located
        • Offset
    • Collar damage  (ES March/April 2010; CW 1/25/10, 4/16/12, 6/17/19)
      • Horizontal abrasion (CW 1/25/10, 4/16/12)
      • Vertical abrasion (CW 6/17/19)

Hubbed-In debris (CW 5/27/13)

Deformed collar (CW 12/18/20)

Clashed dies (ES March/April 2002; CW 3/22/10, 4/30/12)

Collar clash  (CW 6/11/07, 2/24/22)

Die damage with design transfer

    • Floating die clash (ES May/June 2002, May/June 2005; CW 7/19/10)
    • Floating (Type 2) counterclash (ES May/June 2002, July/August 2002, Sept/Oct 2002, Jan/Feb 2009, Sept/Oct 2011; CW 9/29/08, 12/13/10, 4/9/12, 4/21/14, 6/8/15, 4/23/18, 2/21/22, 12/19/22, 2/20/23)
      • COIN WORLD SPECIAL: article posted HERE
    • Miscellaneous and unexplained forms of design transfer/duplication
      • Some presumed Canadian counterclashes may prove to be something else

Die deterioration/deformation errors

Die breaks

Die exfoliation errors (CW 10/19/20)

 Collar breaks (collar cuds) (ES May/June 2008; CW 11/22/10, 5/17/10, 11/22/10, 12/19/16)

 Die cracks (CW 4/25/16)

Split dies (ES Jan/Feb 2006; CW 6/2/03, 4/10/06, 4/17/06, 6/20/11, 5/11/15, 9/17/18, 4/26/21, 4/18/22, 7/18/22)

Part V. Planchet Errors:

Alloy errors

Subsurface Corrosion (CW 12/21/15)

    • Plated coins
      • Copper-plated zinc cents
    • Solid coins

Rolling Mill Errors

Blanking and Cutting Errors

Upset Mill Errors

    • Coins struck on blank (“Type I planchet”)
    • Abnormally weak upset (ES July/August 2005)
    • Abnormally strong upset (best seen on off-center strikes)
    • “Groovy edge” (possibly from worn groove in upset mill)
    • Variation in cross-sectional shape of rim/edge junction of planchet
    • Struck coin sent back through upset mill
    • Abnormal upset  (ES Sept/Oct 2005; CW 2/27/12, 11/21/16)
      • Wide, flat edge
      • Smoothly convex edge
      • Abnormally wide proto-rim
    • Squeezed-in debris (upset mill inclusion) (ES May/June 2006; CW 9/6/10)
      • Foil-like metal wraps around edge onto one or both faces
        • e.g. Copper foil on nickels (not from improper annealing)
      • Metal wire wraps around edge onto one or both faces
      • Pellet embedded in edge  (CW 9/6/10, 9/22/14)

Edge design errors (impressed into planchet before strike) (includes security edge errors) (CW 6/27/16)

    • Edge design missing
    • Edge design present on normally plain edge (CW 6/27/16)
    • Wrong edge design
    • Edge design too high or too low
    • Interrupted edge design
    • Tilted edge design
    • Broken edging die (CW 6/27/16)

Mispunched center holes (foreign only) (CW 1/7/19)

    • Misaligned holes
    • Double punched center holes
      • One hole centered
      • Both holes misaligned
      • Overlapping holes
      • Totally separate holes
    • Irregular center holes
    • Abnormally small hole
    • Partial hole (from broken hole punch)
    • Circular Indentation (partial penetration)
      • Due to broken-off punch tip
    • Unpunched center hole
    • Hole punched in planchet meant for a solid coin

Annealing Errors

    • Improper annealing (due to excessive heat, prolonged exposure to intense heat, or excessive oxygen in annealing oven) (replaces “sintered plating” and “copper wash”) (ES July/Aug 2010; CW 11/30/09, 2/8/10)
      • Black, brown, red, coppery discoloration (includes “black beauty” nickels)
      • Layer of copper, often peeling

Poorly annealed or unannealed planchets (hard, brittle planchets) (CW 3/14/11)

    • Broken planchets and coins (CW 3/14/11, 9/18/23)
    • Radial cracks in coin (usually struck out-of-collar)

Brittle coins (cross-classified with alloy errors) (CW 3/14/11)

Abnormally hard planchets (CW 12/17/12, 8/15/22)

On undersized or underweight planchets (CW 2/13/12)

Miscellaneous forms of mint discoloration

Plating Errors

Bonding/Bonding Mill Errors (ES Sept/Oct 2002)

Irregular planchets

Pristine Planchets (i.e. lacking tumbling marks) (CW 1/11/16)

Pre-Strike Damage (CW 11/15/10, 11/15/10, 1/23/12, 1/30/12, 12/15/14, 4/13/15, 6/8/20)

    • COIN WORLD SPECIALS: articles posted HERE and HERE
    • Assay clips (cross-classified with blanking errors)
    • Rim burrs (CW 1/31/11)
    • Accidentally and intentionally “re-sized” planchets (CW 9/15/10)
    • “Crimp marks” (mostly found on off-metal errors, e.g., 5c/1c, 5c/10c)
    • Rockwell test mark in planchet  (circular or oval dimple) (ES July/Aug 2006; CW 10/15/18)
    • Planchet with adjustment marks (gold and silver planchets filed to return heavy planchets to normal weight)
    • Edge rolled, squeezed, and folded-over (or with thin apron produced) (CW 11/15/10, 1/23/12, 6/15/20)
    • Pre-plating damage (zinc cents) (CW 1/23/12)
    • Post-plating damage (zinc cents) (CW 11/15/10)
    • Scraped-in debris  (CW 2/23/15)
    • Repetitive pre-strike damage (CW 12/15/14)
    • Other forms of pre-strike damage
      • Gouged (CW 1/14/19)
      • Crushed (CW 4/13/15)
      • Scraped (CW 2/23/15)
      • Torn
      • Crumpled (CW 8/15/11)

Inter-strike Damage (CW 1/9/12, 8/20/12)

    • Cancelled or defaced between strikes (CW 3/25/13)

Trans-strike damage (CW 7/12/21)

Wrong planchet and off-metal errors

Bi-metallic errors (foreign only) (ES Nov/Dec 2005)

    • Misaligned core  (ES May/June 2007; CW 3/6/23)
    • Misaligned center hole (ES Sept/Oct 2007)
      • Well-seated core (CW 3/6/23)
      • With misaligned core (CW 3/6/23)
    • Double-punched center hole
    • Unpunched center hole
      • Solid disc of ring metal (CW 3/26/18)
      • Solid disc of ring metal with embedded core
      • Solid disc of ring metal with core indent
    • Ring with incomplete punch  (ES Sep/Oct 2007)
    • Core with incomplete punch
    • Struck outer ring  (ES Jan/Feb 2007)
    • Struck core  (ES Nov/Dec 2006)
      • From another denomination
      • From another country (ES Sep/Oct 2009, Nov/Dec 2011)
      • Struck by solid-denomination dies
    • Wrong core inserted  (ES Sep/Oct 2013; CW 10/17/22)
      • Core-sized scrap disc of ring material inserted into disc
    • Wrong ring  (ES March/April 2007; CW 10/10/22)
    • Ring accidentally punched from solid planchet
    • Ring accidentally punched from solid coin  (ES Nov/Dec 2008)
    • Struck ring from another country (restruck)
    • Struck core from another country (restruck)
    • Unstruck core inserted into struck ring and then restruck
    • Abnormally small core (controversial)
    • Abnormally wide center hole (controversial)
    • Abnormally thin core
    • Abnormally thick core
    • Abnormally thin ring
    • Abnormally thick ring
    • Incomplete trilaminar core
      • Missing one layer (ES Mar/Apr 2010)
      • Missing two layers
    • Core punched out of ring strip
    • Ring punched out of core strip
    • Bi-metallic planchet struck by solid-denomination dies
    • Solid-denomination planchet struck by bi-metallic dies (ES Mar/Apr 2014)
    • Bi-metallic planchet struck by wrong bi-metallic design

Part VI. Striking Errors

Unstruck blank (“Type I”)

Unstruck planchet (“Type II”)

Die alignment errors

    • Rotated die errors (CW 6/21/10, 7/9/12)
      • Rotated die due to improper installation (fixed rotation)
      • Rotated die due to improper die preparation (fixed rotation)
        • (e.g., grinding flats in wrong spot)
      • Rotated die due to movement after installation (dynamic rotation)
      • Semi-stable rotated die errors (various causes)
        • Characterized by a limited range of motion, a limited number of positions, or the presence of a single dominant position (CW 7/9/12, 8/7/23)
    • Pivoted die errors (probably involves entire die assembly) (CW 6/22/15, 10/21/19)
    • Alignment with off-center strikes (CW 8/19/19, 8/26/19)
    • Horizontal misalignment (CW 10/27/03, 7/25/16)
      • Hammer die (CW 2/1/10, 6/25/12)
      • Anvil die (ES Sept/Oct 2004, March/April 2005; CW 9/27/10, 1/19/15, 1/4/21, 7/19/21)
        • With misaligned collar
        • With broken collar
      • Dynamic misalignment (CW 6/25/12, 11/23/20)
      • Multiple misaligned strikes (CW 10/11/21, 11/29/21)
      • Stable misalignment
      • On double-struck coins
        • On first strike only (CW 8/31/20)
        • On second strike only (CW 5/19/08, 5/23/11, 9/19/13)
        • On both strikes
        • Alignment with off-center strikes (CW 8/19/19, 8/26/19)
  • Vertical misalignment (tilted die error) (ES Jan/Feb 2003, Sept/Oct 2003; CW 12/8/03, 12/20/10, 8/24/15, 10/24/16, 1/8/24)
    • Hammer die (CW 2/1/10, 6/17/13)
    • Anvil die
    • Dynamic misalignment (CW 10/24/16)
    • Stable misalignment (CW 1/29/14)
    • Associated with weak strike (? 2/1/10, 10/8/12, 8/16/21)
    • Associated with off-center strike (? 8/13/18)
  • Dual misalignments (dies often misaligned in different directions) (CW 11/28/11, 5/18/15, 1/9/17, 7/9/18, 8/26/19)
  • Compound misalignments (CW 8/24/15)
    • Horizontal and vertical
    • Horizontal and rotated
    • Rotated and vertical
    • Horizontal, rotated, and vertical (CW 8/26/19)
  • Forced misalignments (CW 8/28/17)

Collar alignment errors

  • Misaligned collar
    • Associated with misaligned anvil die
    • Associated with stiff collar error
    • Associated with elliptical strike clip
  • Rotating collar (detectable only when there’s a collar break and a multi-coin progression)

Collar deployment errors

    • Partial collar (CW 2/24/20)
      • Flange with bevel
      • Flange without bevel
      • Tilted partial collar
      • Undulating partial collar (CW 2/24/20, 7/25/22)
      • Re-entry partial collar
      • Incomplete ejection partial collar (CW 12/26/22)
      • Reversed partial collar (not an error)
      • Multiple steps (CW 3/15/21)
    • High deployment of collar with coin metal extruded beneath (doubtful)
    • Broadstrikes
    • Stiff collar errors (ES Nov/Dec 2000; CW 8/25/08)
      • Normal die installation
      • Inverted die installation
      • Association with misaligned dies
      • Association with misaligned collar
      • Strong collar scar
      • Strong collar scar with cupping
      • Planchet forced completely into fully deployed collar (“ram strike”) (ES Nov/Dec 2000, March/April 2001)
      • Elliptical strike clip (ES March/Apr 2000; CW 4/5/10)
      • Associated with weak strike (CW 2/11/13)
    • Collar shimmy (CW 8/21/17, 9/11/17)

Weak Strikes (ES Sept/Oct 2000; CW 5/3/04, 9/11/06, 6/18/07, 3/1/10, 5/23/11, 6/23/14, 8/27/18, 3/2/20, 10/26/20, 11/27/23)

    • Caused by insufficient die approximation
    • Caused by abnormally low ram pressure
    • Invisible strikes (ES March/April 2003, Nov/Dec 2003, March/April 2004, Nov/Dec 2006, May/June 2010; CW 5/3/10, 9/20/10)
      • With indent
      • With partial brockage
      • With struck-through error
    • Followed/preceded by strong strike (CW 7/13/20)
    • Stable series of weak strikes (CW 8/27/18)
    • Weak saddle strike
      • One strike weak, one strong (CW 4/8/13)
      • Both strikes weak (CW 12/12/11)
    • In combination with other striking errors
    • Rim-restricted first strike (CW 3/1/10, 10/10/11, 1/11/16, 2/19/18, 9/23/19)
    • Rim-restricted second strike (CW 9/21/15, 2/13/17)

Skidding Coin Errors (CW 1/29/18)

Abnormally Strong Strikes

Stutter Strikes (ES Nov/Dec 2001, Sept/Oct 2007; CW 12/28/09, 7/25/11, 8/10/20)

    • Due to spasmodically collapsing or stiff collar (Type I)
    • Due to planchet flexion (associated with indents and brockages) (Type II)
    • Due to contact with bent planchet or coin (Type III)
      • On face struck by anvil die (CW 8/26/13)

Concentric strike lines generated by a single strike (ES Jan/Feb 2012; CW 12/26/11)

Machine doubling (a.k.a. machine doubling, machine doubling damage, machine damage doubling, mechanical doubling, strike doubling, shift doubling, ejection doubling) (ES July/Aug 2006; CW 3/15/10, 7/24/17, 12/23/19, 3/30/20)

    • “Push doubling” (marginal shelving and sharp interior duplication) (CW 1/9/23)
    • “Slide doubling” (smeared design) (CW 8/14/17)
    • Rotational machine doubling  (CW 8/10/15)
    • Intermediate forms
    • Multiple machine doubling in one direction (two, three, and four offset ranks)
    • Machine doubling in more than one direction (up to three directions)
    • Machine doubling on both faces of same coin  (CW 3/15/10, 12/23/19)
    • Rim-restricted design duplication (see separate category)
    • Affecting incuse design elements (CW 2/6/06, 1/16/12)
    • Located on top of die break
    • Located on top of die attrition error (CW 4/14/14)
    • On out-of-collar strikes (rare) (CW 11/25/19, 11/21/22)

Rim-restricted design duplication (form of machine doubling) (CW 10/6/03, 2/22/10, 5/24/10, 12/6/10, 5/13/13, 12/30/13, 3/8/21, 4/12/21)

    • 2004 cent (ES March/April 2007; CW 2/22/10)
    • 1994 cents (CW 5/24/10, 8/22/11)
    • 1981-P quarter and 1979-D dime (CW 12/30/13)
    • Presidential dollars (ES Sept/Oct 2007; CW 2/22/10, 12/6/10)
    • Foreign coins (CW 2/22/10)
    • On face struck by anvil die (CW 10/21/13, 7/20/20)
    • Bifacial (CW 7/20/20)
    • In conjunction with push doubling (CW 12/6/10, 7/20/20)

Ejection Doubling (CW 11/7/22)

Skidding Die Errors (CW 8/15/16, 11/27/17)

    • Design decapitation error (top of design scraped off)
    • Slide doubling  (see Machine Doubling)
    • Design ablation error  (design scraped off by die movement on 2nd strike) (ES March/April 2008, Jan/Feb 2011; CW 9/13/10)
    • Combined with tilted die (CW 9/27/21)
    • From broken die (CW 7/26/21)
    • Skidding misalignment
      • Two-stage (CW 4/13/20)

One-sided double-strikes (ES March/April 2000, Jan/Feb 2002, July/August 2003)

    • Hammer die rotated (CW 11/29/10)
      • Instantaneous
      • Gradual
    • Hammer die misaligned (CW 5/19/08, 5/3/11, 9/9/13, 3/8/21, 4/24/23)
      • Instantaneous
      • Gradual
    • Anvil die misaligned (CW 9/9/13, 8/31/20)
    • Anvil die rotated (at least one known example, a proof Kennedy half dollar)
    • Rotated, with rocking die (CW 5/25/20)
    • False one-sided double strikes (CW 11/29/10)

Flat Field Doubling (imperfectly aligned proof strikes) (CW 4/29/13)

Off-center strikes

    • Cupped off-center strikes
      • With collar scar
      • Without collar scar
    • Uniface strikes
    • Stretch strikes
      • Uniface
      • Die struck on both faces (covered under high pressure strikes)
      • With unexplained, flat dent at opposite pole (not a “sideneck strike”)

Chain strikes (CW 4/12/10)

    • Normal chain strikes with straight edge
    • External chain strikes (ES Jan/Feb 2003)
    • Concave, convex, sinuous, and irregular chain strikes (ES Jan/Feb 2001, July/August 2002; CW 4/12/10)

Foreign Object Chain Strike (CW 5/25/15)

    • Chain strike against feeder

Machine Part Impingement  (CW 5/25/15)

    • Bilateral
    • Unilateral

Saddle (Tandem) Strikes (CW 6/27/11)

    • Hump present
    • Hump absent
    • Inverted hump (hump points toward reverse die) (CW 9/19/16)
      • Buckling toward anvil die
      • Due to inverted die setup
    • Die position
      • Head-to-head
      • Head-to-base (early to mid- ’70s, mainly)
      • Face-to-back
      • Other orientations
    • Gap between adjacent dies
      • Narrow
      • Wide
    • With inverted die installation
    • Sideneck strikes (“one-die saddles”) (Expanding planchet collides with side of die neck) (CW 5/30/11)
    • On quarter dollars (CW 12/9/19)

Broadstrikes

  • (covered under collar deployment errors)

Split Plating Doubling

Foldover Strikes (ES July/August 2007; CW 10/10/05, 8/15/11, 1/30/12, 9/15/14)

    • Out-of-collar
    • In-collar
    • With edge strike persisting
    • On struck cents (normal and error)
    • Double foldover strikes (“Z-fold”)
    • Axial fold
    • Paraxial fold
    • Inward fold
    • Outward fold

Edge Strikes (CW 7/18/11, 10/12/15, 3/1/21)

Extrusion strikes (an effect, not an independent error) (ES March/April 2004; CW 10/24/11, 1/15/18)

Multiple strikes (CW 3/30/15)

Indents

    • In-collar/out-of-collar
    • Partial
    • Full (CW 7/30/12)
      • Centered
      • Uncentered
    • “Internal” indents (CW 11/1/10, 2/28/16)
      • On obverse
      • On reverse
    • Multiple indents
    • Irregular indents
      • Produced by error coins
      • Produced by clipped planchet
    • Unexpectedly shallow indents (CW 12/28/20)
    • Indent by smaller planchet  (CW 5/19/08)
    • External disc impressions  (CW 3/18/19)

Brockages

    • Full
      • Centered
      • Uncentered
      • Rotated (relative to die-struck design on opposite face)
    • Partial
      • Conventional
      • Aligned partial brockage (ES May/June 2005; CW 1/17/11, 12/5/22)
        • From partial die cap
        • From elliptical clip coin
        • From elliptical strike clip
      • Internal partial brockage (CW 11/1/10)
    • In-collar/out-of-collar
    • From another denomination (ES May/June 2005; CW 8/1/21)
    • From another error coin
      • From wrong planchet error (CW 11/28/22, 6/12/23)
      • From mangled and crumpled coins (often multi-struck) (CW 10/2/23)
      • From weakly-struck coins (CW 11/20/23)
    • Flipover brockage (CW 4/23/12)
      • On obverse
      • On reverse
    • First-strike brockage
      • “Mirror” brockage (unexpanded, undistorted) (CW 6/13/11, 3/17/14, 5/6/19, 10/28/19, 7/11/22, 6/27/22, 4/10/23)
      • Distorted first-strike brockages
    • Mid-stage and late-stage brockages
    • By struck fragment (CW 6/11/12)
      • Aligned with opposite, die-struck design
      • Not aligned with opposite design
    • From struck die fill (very rare) (CW 8/20/18)
    • From thin pieces of metal (CW 7/23/18)
    • From large dropped filling (CW 5/13/19)
    • Multiple brockages (CW 9/26/11)
      • From multiple strikes
      • From clashed cap
      • From multi-struck coin (CW 7/4/22)
      • From more than one coin in striking chamber
      • From coin trapped between die cap and planchet
    • Clashed cap strikes (CW 8/30/10, 11/21/11, 1/13/14)
      • From a late-stage die cap that clashed with the opposite die
      • From a uniface die cap that clashed with the opposite die
      • From an early-stage die cap that clashed with the opposite die
      • From a cap that was striking counterbrockages that clashed with the opposite die
      • From a flipover die cap that clashed with the opposite die (CW 1/13/14)

Counterbrockages

    • Full (CW 10/11/10)
    • Partial (CW 11/8/10)
    • In-collar/out-of-collar
    • Counterbrockage of obverse on obverse
    • Counterbrockage of reverse on reverse
    • Flipover counterbrockage (CW 4/19/21)
    • Early, middle, and late-stage counterbrockages
    • From another error coin
    • Brockage-counterbrockage combination (8 types) (ES Nov/Dec 2009; CW 11/12/12)
    • Multiple counterbrockages (ES March/April 2010)
    • On second strike
    • Rebound counterbrockage (always on 3rd strike) (CW 11/9/15)
    • Secondary counterbrockage (CW 4/19/21)
    • Grease-generated counterbrockage (CW 4/11/22)

Horizontal lipping (CW 11/30/15)

    • In conjunction with in-collar indents, partial brockages, and struck-through errors

Die caps (CW 8/6/13, 1/7/20)

    • Hammer die caps (usually the obverse die)
      • Raised design on working face
      • Brockage on working face
      • Uniface die caps
      • Complex die caps
    • Anvil die caps (usually the reverse die)
      • Cupped toward anvil die, hammer die, both dies at opposite poles, or expanded in the horizontal plane
    • Partial (off-center) die caps (hammer or anvil) (CW 1/17/11)
      • With cupping
      • Without cupping
    • Detached cap bottoms (ES March/April 2001, May/June 2001)
    • Clashed caps (CW 1/22/24)

Capped die strikes (generic — without identifiable images)

    • Struck by uniface die cap
    • Struck through late-stage die cap
    • Struck through cap-like obstruction
    • Struck through split or torn cap
    • Proportional de-expansion (both faces struck through die cap or cap-like obstruction) (CW 11/11/13, 5/28/18)

Struck by impaled die cap (CW 6/10/13)

Capped die doubling (doubling associated with capped die strikes) (ES Sept/Oct 2005; CW 6/18/12, 5/16/22)

    • Shifted/rotated cap strikes (ES May/June 2000, March/April 2012; CW 11/21/11)
      • Correctly-facing incuse design elements (CW 11/3/08, 6/28/10, 6/11/12, 10/19/15, 8/12/19, 10/23/23, 11/13/23)
        • Multiple sets due to several preceding shift-and strike event
    • Unexplained, close raised doubling
      • Expansion ripples
    • Incuse doubling surrounding raised elements (CW 8/24/20)

“Struck-through” errors

    • Struck through fragment
    • Struck through clipped planchet (ES Sept/Oct 2002; CW 8/25/14)
    • Struck through thin struck fragment (CW 6/11/12)
      • Face-up (correctly-facing incuse design elements)
      • Face-down (mirror-image design elements)
      • Trapped between planchet and opposite die (mirror-image design elements)
    • Struck through detached lamination flake (CW 2/7/05, 6/11/12)
    • Struck through clad layer
      • Clad layer unstruck
      • Clad layer previously struck
    • Struck through reeding (CW 11/14/16, 8/21/23)
    • Struck through split planchet
      • Obverse
      • Reverse
    • Struck through hardware  (bolts, screws, washers, etc) (CW 3/7/11)
    • Struck through feeder (ES Nov/Dec 2005; CW 3/7/11)
    • Struck-through unidentified machine part (CW 3/7/11)
    • Struck through emery disc (CW 12/16/02)
      • 1986 Silver Eagles struck through emery disc (CW 12/16/02)
    • Struck through “grease” (die fill)
      • Assorted ingredients, textures, viscosities, and consistencies (smooth, coarse, stiff, viscous, etc.)
    • Filled dies
      • Single design element (CW 6/29/20)
      • Multiple design elements
    • Struck through bulging die filling (CW 1/16/17, 5/20/19)
    • Filled collar/obstructed collar (ES Jan/Feb 2006; CW 9/22/14)
      • With flange
    • Surface Film Effects (ES May/June 2003; CW 8/16/10, 6/11/12, 10/29/12)
      • Surface film doubling
      • Surface film afterimage
      • Surface film transfer
      • Surface film transfer with clash marks
    • Dropped fillings (ES May/June 2003; CW 8/16/10, 6/11/12, 10/29/12)
      • Isolated elements (dropped letter, dropped number) (CW 2/7/05)
      • Conjoined dropped fillings (CW 8/16/10)
      • Large, multi-element dropped fillings (CW 4/19/10, 8/16/10, 11/14/22)
      • Retained dropped fillings
    • Struck through floating encrustation  (on second strike) (CW 1/18/16, 6/18/18)
    • Yanked-out fillings (CW 1/16/23)
    • Struck through miscellaneous foreign matter
    • Field-restricted struck-through errors  (CW 11/18/13)
    • Split or torn in two by struck-thru object (ES Nov/Dec 2007; CW 3/7/11, 7/13/15)
    • Retained struck-through errors (struck-in errors) (CW 7/18/16, 1/25/21, 9/13/21)
      • Embedded dropped filling (see above)
      • Embedded die fill (shapeless)
      • Die fragment (CW 2/6/23, 3/13/23)
      • Scrap metal
      • “Staple” (bristle from wire brush)
      • Plastic (associated with bullion coins)
      • Metal foil
        • (Cu-Ni)? associated with dimes and nickels)
        • Copper foil  (ES Nov/Dec 2007)
      • Rubbery material (from die cover?)

Uniface strike (cross-classified with indents) (CW 7/30/12, 9/16/19)

  • In-collar (CW 12/5/22)
  • On second strike (CW 11/29/10, 9/16/19, 6/5/23)
  • “Augmented” in-collar uniface strikes (CW 9/14/20)
    • Out-of-collar
      • Centered
      • Off-center

Sandwich strike (coin struck between two coins or planchets) (CW 5/16/11, 10/31/16, 11/20/17, 5/28/18, 3/22/21)

    • Partial
    • Full
    • Between two struck coins
    • Between two planchets
    • Between a coin and a planchet
    • Between struck coin and obverse die cap
    • Between obverse and reverse die cap

Nested coins (CW 3/16/20)

Mated pairs (CW 11/9/20)

Bonded coins   

    • Pile-ups (clusters)

Strike clips (ES July/Aug 1999, May/June 2001; CW 6/15/15)

    • Vertical shear clips (V)
      • Sheared between die and collar alone
      • Sheared between collar and overlying planchet
    • Horizontal shear clips (H)
    • Tensile strike clips (T)
    • Concave strike clips (V, H, T)
    • Elliptical strike clips (V, H, T) (CW 4/5/10, 12/5/22)
    • Straight strike clips (H)
    • Saddle strike/strike clips (H)

Detached reeding

    • From forced broadstrikes
    • From stiff collar
    • Torn-off fin

Coin shrapnel (“breakaway fragments”)

    • Angular
    • Crescentic
    • Oval
    • Circular or sub-circular
    • Semilunar
    • Irregular

Intra-Strike Damage (damage coincident with strike) (CW 5/30/2011, 12/20/21)

    • Flat contact facet at 6:00 opposite off-center strike
    • Machine part impingement on unstruck portion of off-center coin (CW 5/25/15)
    • Ejection damage to edge of unstruck perimeter.
    • External struck-through errors (with cupping) (CW 3/25/19)
    • Concave damage opposite off-center strike (CW 12/30/19)

Cupping (CW 12/7/09)

    • With and without collar scar
    • In a single strike
    • Associated with multiple strikes
    • With die caps
    • Cupping toward hammer die
    • Cupping toward anvil die
    • Expansion in horizontal plane
    • On unobstructed strikes (CW 3/18/19)

Impact-Induced Warping   (CW 3/16/15, 1/13/20)

Malrotation Errors (multi-sides coins only) (CW 3/23/15, 11/8/21)

Proof edge lettering errors (generated during strike by segmental collar)

    • Weak edge design due to segmented collar not closing fully (wide seams)
    • Segments arranged in incorrect sequence (see Die Installation Errors) (CW 4/7/08)

Part VII. Post-Strike Mint Modifications

Edge lettering applied after strike (incuse) (small dollar coins)

    • Absent lettering  (CW 4/26/10)
      • Due to bypassing the lettering device
      • Due to excessive spacing between steel wheel and lettering die
    • Vertically misaligned letters (cut off at top)
    • Vertically misaligned letters (cut off at bottom)
    • Wrong spacing between incuse design elements
    • Obliquely-oriented lettering
    • Overlapping letters
    • Two sets of letters
    • Skipped letters
    • Letters on wrong planchet
      • 2007-D Sacagawea dollar with Presidential edge lettering (CW 7/9/12)
    • Chipped letter
    • Lightly impressed letters (weak lettering) (CW 4/26/10)
    • Unusually deep letters (coin squeezed too hard, leaving a rippled margin)
    • Incomplete letters
    • Smeared letters
    • Edge letter font subtypes (CW 10/18/10)
    • Wrong date on edge (doesn’t match any President of that year) (CW 2/22/10, 3/1/10)
      • 2009 Zachary Taylor dollar with 2010-D edge inscription (CW 2/22/10, 3/1/10)
    • Edge lettering on unstruck planchet (CW 3/26/07, 3/17/08)
    • Lettering die inclusion   (CW 9/14/15)

Note: Edge lettering and other edge design elements may be impressed during upsetting, during the strike, by a special machine before the strike, or by a lettering device after the strike. Similar-looking defects can occur in each of these processes. Any edge design that forms a closed interlock between the edge of the coin and the collar cannot be produced during the strike since that will prevent ejection of the coin after the strike.

Special Note: Some presidential dollar coins have had the edge lettering removed outside the mint. Use caution when buying any edge lettering error.

The diagnostics for authentic presidential coin missing its edge lettering are as follows:

1. Diameter should be 26.46 mm. Coins altered outside the mint will have a diameter that is less than 26.46 mm and will have a diameter of approximately 26.21 mm.

2. The coin’s weight should be approximately 7.98 g ± .03 g. Altered coins will weigh less from the removal of the edge lettering. Weights of approximately 7.89 g are commonly seen on altered coins.

3. An unaltered presidential dollar coin will have vertical lines along the edge. These lines are created when the coin is ejected. Altered coins will not normally have these lines, but instead will have horizontal lines. These horizontal lines are from milling or similar machines used outside the mint to remove the letters and are the aftereffects of the metal being abraded off the coin.

67400692

The above image shows the vertical lines present on the edge of an unaltered presidential dollar coin with no edge lettering

Table of edge lettering errors found on the presidential and native American dollar coins

Post-strike chemical treatment

Matte or frosted finish applied after strike

    • Finish omitted on one or both faces (CW 8/1/11, 8/29/11)

Part VIII. Post-Strike Striking Chamber Mishaps

Post-strike die contact

  • Ejection impact doubling (post-strike design transfer from die) (ES Jan/Feb 2005; CW 8/1/05, 8/29/05, 2/25/13, 2/26/18, 4/9/18, 10/8/18, 4/12/21)

Ejection damage

Part IX. Post-Strike Mint Damage

Illicitly applied die impressions (CW 11/16/20, 1/4/21, 2/1/21, 8/29/22)

Pseudobrockage (false brockage) (ES Nov/Dec 1999; CW 8/23/10)

Fused coins

Rolled and squeezed

Accidentally resized

Other (folded, crushed, scraped, bent, etc.)

Intentional damage (e.g., canceled, waffled)

Zinc deterioration on copper plated Lincoln cents

Part X. Wastebasket/Composite Categories

Ghost images (CW 8/1/11)

    • Progressive, indirect design transfer   (a.k.a. internal metal displacement phenomenon, ghosting, heavy design transfer) (CW 6/7/10)
    • Worn clash marks
    • Thin planchet (CW 8/2/10)
    • Split planchet (CW 8/31/15)
    • Coin thinned by strike(s)
    • Weak strike (CW 4/11/11)
    • High pressure strike
    • “Greasy ghost”   (CW 7/5/10)
    • Surface film afterimage (CW 5/2/11)
    • Surface film transfer (CW 5/2/11)
    • Split plating afterimage (CW 5/2/11)
    • Coarsened crystallite afterimage (CW 5/2/11)
    • Slide zone ghost letters (? 11/16/15)
    • Incuse ghost images associated with capped die strikes (CW 10/25/21)

Doubling

Embedded matter (CW 12/14/09)

Edge overhangs (CW 11/30/2015)

    • Partial collar errors
    • Horizontal lipping
    • Stiff collar errors
    • Forced broadstrikes

Part XI. Non Errors:

Counterfeit Coins

Fabricated or Altered Errors

Damaged Coins

    • Chemical corrosion
    • Environmental discoloration and corrosion
    • Crushed
    • Bent
    • Impact damage
    • Stacked coins crushed and fused in equipment

Enhanced Errors (genuine errors subsequently altered to look more exotic)


The End of the Check List

Extrusion Strikes With Indents & Partial Brockages

PART VI. Striking Errors:

Extrusion strikes

Definition: An extrusion strike occurs when coin metal bulges into a gap, rising to meet the die. The result is a limited area of die-struck design restricted to what was the apex of the bulge. An extrusion strike is an effect, rather than an independent error. Extrusion strikes occur in association with partial brockage errors, indents, struck-through errors, and retained cuds.

The 1983 quarter shown below was struck through a torn, dislodged, and laterally shifted late-stage die cap. Coin metal bulged into the triangular tear, meeting the obverse (hammer) die on its way down. The result was a weak strike on the top of the bulge which left the base of Washington’s bust and some of the date. The corresponding area on the opposite face is sunken and featureless.

The 1999 New Jersey quarter shown below has an extrusion strike in association with a partial collar error and a 90%
indent.  Coin metal bulged into the crescent-shaped gap between the intrusive coin and the collar.  The apex of the bulge met the hammer (obverse) die in mid-descent, leaving a strong crescent of die-struck design.  The corresponding area on the reverse face is sunken and featureless.

Below is a 1980 Mexico 20 pesos coin with an 80% partial counterbrockage on the obverse face. Beyond the counterbrockage is a crescent of die-struck design. The design is all there, albeit a tad weak toward the left side. The corresponding area on the reverse face features a crescent of unstruck metal that preserves the original surface texture of the blank planchet. This unstruck area is slightly recessed, as expected. The rim, however, is well struck on the reverse and the beads just inside it are also quite clear. The edge and edge lettering are also very well-struck. There is a very thin partial collar lip running along most of the edge, but the coin was still almost completely confined by the collar.

This extrusion strike developed as coin metal squeezed into the gap between the overlying error coin and the collar. Compressed from all sides in the horizontal plane, the metal buckled and piled up against the obverse die as it simultaneously lifted away from the reverse die. As the coin was struck, the edge of the planchet collided with the collar, and the rims were struck by both dies in a relatively normal fashion, along with the beads on the reverse.
The 5 rupee Indian coin below is indented on the reverse face which was struck by the hammer die. Adjacent to the indent is a crescent of struck die-struck design. The obverse face (lion motiff) shows an unstruck crescent that lies exactly opposite the die-struck design on the reverse face. The presence of die-struck design on only one face is the result of an extrusion strike.

 The obverse face of this 2010 India 5 rupees coin seen below was struck through a clipped planchet.  Both planchets were confined by the collar.  Coin metal bulged through the gap between clip and collar and contacted the reverse (anvil) die, producing an oval of die-struck design.  A featureless pucker lies opposite that patch of die-struck design.
01b_India_5rs_2010_stk_thru_clipped_plan_rev01a_India_5rs_2010_stk_thru_clipped_plan_obv

Die Chips

Part IV. Die Errors:

Die Breaks:

Die Chip:

Definition:  A small piece (less than 4 square millimeters) that falls out of the die face and has no direct connection to the design rim.  The missing piece leaves a void in the die face into which coin metal flows.  As a result, the coin shows a featureless lump in the affected area.

A die chip can be connected to a die crack or it can be freestanding.  Die chips frequently develop within narrow interstices in the design, such as the gap between the letters of LIBERTY.  Hence the so-called “BIE” errors.

This 2007 cent displays a fairly substantial die chip in Lincoln’s hair.  A short die crack extends from one corner of the chip.

Die Crack Rim To Rim

PART IV. Die Errors:

Die Cracks:

Rim to Rim

Definition: A die crack that extends from one point on the rim to another.  A rim-to-rim die crack can more-or-less bisect the die face.  In that case we can designate it a median or bisecting rim-to-rim die crack.  A rim-to-rim die crack can also be located well off to one side.  In that case we can designate it an asymmetrical rim-to-rim die crack.

The course of a rim-to-rim die crack can be straight, irregular, or curved.

A curved rim-to-rim die crack is sometimes called a “pre-cud die crack” even though there’s no guarantee that it will progress to a cud (marginal die break).

A rim-to-rim die crack will typically show lateral spread, leaving a thin raised line on the coin.  In some cases, a segment of the die crack will exhibit slight vertical displacement. If the entire die crack exhibits vertical displacement, horizontal offset, or a mixture of the two, it is designated a retained cud.

A rim-to-rim die crack can worsen and extend deep into the die neck.  This allows the sides of the crack to spread apart.  If the raised line on the coin is unusually wide, it is usually designated a “split die”.  The threshold separating a rim-to-rim die crack from a split die is subjective and arbitrary.  Mike Diamond considers any split wider than 0.5 mm to be a split die.

The image above of a 1941-S Jefferson nickel shows a bisecting, rim to rim die crack. The die crack wich begins above the B in PLURUBS transits downward through the dome of Monticello and into the field below that building. The termination point of the die crack is through the O in the word OF and into the rim.

For more rim to rim die cracks see HERE

Die Dent

PART IV. Die Errors:

Die Damage:

Die Dent

Definition: An area of the die is damaged by a known or unknown object, which leaves a recess in the die face.  The die dent therefore appears raised on the coin.

The reverse die of this 1991(P) Lincoln cent shows the affects of a dent die. A raised anomaly is seen running from the A of STATES, through the PL of PLURIBUS, the UN of UNUM and down to the roof of the Lincoln Memorial building. In this case, the nature and origin of the object that caused the die dent is unknown.

This coin is courtesy of Joe Koelling.

.

An unusual die dent is seen on a proof 2005-S Kansas statehood quarter pictured below. The dent, indicated by an arrow, resembles a “hoof print” on the right flank of the bison.

This image is courtesy of Chris Machuga.

Die Deterioration Doubling Incuse

PART IV. Die Errors:

Die Deterioration / Deformation errors: 

Die Deterioration Doubling:

Incuse doubling

Definition: Die deterioration (die wear, die fatigue) sometimes produces discernible doubling of affected design elements.  We call this die deterioration doubling (DDD).  Its appearance is highly variable.  It is often raised but can sometimes be incuse.  Incuse DDD is most often seen on copper-plated zinc cents, but does occasionally appear in other issues.  Die deterioration doubling may completely surround an affected design element (like a number or letter) or may be restricted to one side.

Unusual forms of die deterioration and die deterioration doubling often develop on dies that strike zinc cents. Illustrated above is a 1989-D Lincoln cent exhibits swelling of the field on both sides of Lincoln’s bust and the development of a low ridge (“ridge ring”) that runs through in god we trust. The date shows a form of incuse die deterioration doubling that is common on zinc cents but rare on other denominations.

Below are two views of another 1989-D Lincoln cent with incuse DDD, and to the right a 1993 Lincoln cent with incuse DDD above EPU. While altogether different, incuse DDD can visually seem similar to, plating disturbance doubling. While plating disturbance doubling is raised, and the form of DDD illustrated incuse, they often inhabit the same regions of Lincoln cents and seem similar under certain lighting conditions.

Below are images on incuse DDD on a 2007 Idaho State Quarter.

 

Delayed Second Strike

Part VI. Striking Errors:

Multiple Strikes:

Delayed Second Strike

Definition: A delayed second strike is one that is delivered in a different striking chamber or coinage press after a considerable delay.  Coins carrying strikes with two different dates are an obvious example.  In the absence of such an obvious clue, collectors must probe a little deeper.

A delayed second strike will be delivered in a different striking chamber and will therefore carry different die markers.  Die markers are blemishes — often microscopic — that serve to identify a particular die pair.  Die cracks, die scratches, die dents, and die flow lines are just some of the markers to inspect.

Not all coins struck by a different die pair represent a delayed second strike.  Lower denominations (cents, nickels, and dimes) were often struck in dual or quad presses in which die pairs were arranged in adjacent couplets.  A newly-struck coin could easily move from one member of the couplet to another.

For higher denominations, a strike from a different die pair would represent a delayed second strike as the dies were never arranged in adjacent couplets.

A delayed second strike can also be identified by the presence of inter-strike damage of a kind that could not be generated within a striking chamber.

Shown below is a 1985-P quarter with a delayed second strike.  After a normal first strike, the reeding was completely shaved off the edge and the coin was rolled and squeezed to a smaller diameter.  It was then transported to a distant striking chamber (and probably different press) where it received a flipover, off-center, uniface strike.  The die pair that delivered this second strike was characterized by an unstable hammer (obverse) die or die assembly that was swinging from side to side.  This produced an extreme case of collar clash on the left side (the first strike shows no signs of collar clash in the corresponding area.  A swing to the right followed after the hammer die reached the lowest point of its downstroke.  This produced a dramatic case of slide doubling (a form of machine doubling).

Design Extention Dimples

PART II. Die Varieties:

Design Extension Dimples

Definition: Design extension dimples (DED) are raised areas on the working die (indents on the coin) originating from an unknown cause.

While we are unsure of the exact cause of this phenomena, both Mike Diamond and I feel that it is hubbing related. Rather than affix a category (error or variety) to this oddity, we are simple calling it a die anomaly.  The discovery piece is credited to Fred Weinberg and has been encapsulated by ICG. Mike Diamond has also written an article concerning Design Extension Dimples in his column “Collectors’’ Clearinghouse” in Coin World.

If more of this anomaly type are found, which I am sure will happen, a designation will be applied to each individual find. Weinberg’s find will now have the designation of 2011D-100DEDO-001AJ.

The attributes for this anomaly type can be seen as depressions on the coins surface that extend from the peripheral design elements in an inward, radial pattern. Refer to the pictures below of 2011D-100-DEDO-001AJ.

Design extension dimples can also be seen on the reverse die of this 2008D Lincoln cent.

 

 

Design extension dimples can also be seen on the reverse die of this 2010P Jefferson nickel. While this maybe a true die anomaly, it seems to be quite common and found on all denominational coins. Theoretically, design extension dimples will lessen in strength as the die ages. However, the possible use of determining the die’s age by the strength of the dimples is hamper by the fact of not knowing the strength of the dimples at the initial strike.

As for collectibilty, since they are not uncommon, no premium is attached to the anomaly.

Continuing research by Al Lipa has shown that design extension dimples occur in all the denominations, with dimes least frequently affected. The majority of  affected dies with strong DED seem to be produced by the Denver Mint.

 

Design Creep

Part IV. Die Errors:

Die Deterioration/Deformation Errors:

Design Creep

 

Definition: In this rare die deformation error, the die face expands during the press run.  In lateral view, it comes to resemble the battered handle of a rock chisel.  Eventually the die face expands beyond the working face of the collar (presuming the hammer die is involved).  The result is that the face of the coin struck by the deformed die lacks the design rim and the peripheral design elements are cut off.

Among domestic coins, design creep has only been seen in a single run of 2014-P nickels, all of which were discovered by Robert Scheschuk.

02a_design_creep_2014P_5c_rev 02b_design_creep_2014P_5c_obv

The reverse face of this 2014-P nickel (struck by the hammer die) shows the effects of design creep.  The design rim is absent and peripheral letters are cut off along the coin’s edge.  This effect is more severe along the southern arc of the coin.  Additionally, the center of the coin displays a peculiar “cottage cheese” texture.  Here the details of Monticello are indistinct.

Design Scraped Off Ablation First Strike

PART VI. Striking Errors:

Design Ablation Error:

On First Strike

Definition: The die-struck design on the surface of a coin is scraped off by lateral (horizontal) die movement.

This 2001-D Lincoln cent exhibits a design ablation error on the first strike.  The hammer die made initial contact with the planchet in a centered position but settled in a misaligned position.  During its lateral shift toward the northeast, the hammer die continued its descent through the body of the coin.  The completion of the downstroke amounted to no more than a fraction of a millimeter of vertical distance.  The combination of movements (vertical and horizontal) left a crescentic “zone of ablation” on the left side of the coin.  All design elements that were generated by the initial, centered impact of the hammer die were completely scraped off.  The zone of ablation is filled with fine parallel striations and shows a very gentle downward slope that begins at the original design rim.

After reaching the lowest point of its downstroke, the hammer die lurched toward the southwest, dragging itself through the newly-struck design.  This left the design grotesquely distorted.  This form of distortion is classified as a form of machine doubling known as slide doubling.  Design ablation errors that occur on the first strike are usually associated with severe slide doubling.

Design ablation errors on the first strike are usually misidentified as simple misaligned die errors.