Part V: Planchet Errors:

Alloy Errors:

Split planchets, Before strike

Definition: Split planchet errors are normally restricted to planchets composed of a solid alloy.  Among U.S. coins, cents and nickels are the most commonly affected denominations.  Split planchet errors should not be confused with “separation errors”, which only affect clad  and plated coins.  Separation errors are bonding errors, not alloy errors.

A coin struck on a split planchet will always weigh less than a normal coin. A coin struck on a split-before-strike planchet will show a pattern of striations on the split face.  The texture of the striations varies from coarse to fine.  If a strike is unusually strong, most of the striations may be effaced.  However, most split-before-strike planchets show a weak strike, because the thinner planchet is closer to the minimum die clearance.

Shown below is a 1961-D cent struck on a split planchet.  The pattern of striations is unusually coarse.

The two rupee Indian coin below is comprised of a nickel alloy. This planchet weighs 3.2 g, well below the normal 6.0 g. The obverse face has an expected weak strike with much design detail absent. The reverse face shows coarse striations with a combination of weak and strongly struck design.

 Approximately half the reverse face of this 1888 shield nickel peeled off before the strike. This part of the coin was
consequently left too thin for any design to strike up.

Images are courtesy of Heritage Auctions.

PART V. Planchet Errors:

Plating Errors:

Split plating

Definition: Split plating occurs when the copper plating is stretched too thin causing it separate. This separation usually occurs immediately after a design element and has a direction towards the rim of the coin affected.

Below are two views of a Lincoln cent, one of the mintmark on a 1992-D and the other on the reverse showing the memorial roof. In each case, the plating has split exposing the zinc core below which has a bluish hue.

The image above of a 1982-D Lincoln cent show split platting after the 2 in the date and the mintmark. The crystal formation seen below and to the right of the mintmark is Hydrozincite and it is a form of post strike damage.

PART V. Planchet Errors:

Plating Errors:

Split plating doubling

Definition: Best expressed and most often seen among broadstrikes and off-center strikes, split plating doubling is restricted to copper-plated zinc cents.  When the planchet is struck, the portion trapped beneath the dies expands in all directions.  The thin copper plating is subjected to tensile as well as compressive stress.  The tensile stress causes the copper plating to rupture, exposing the underlying zinc.  The exposed zinc often outlines large centrally-located design elements, like busts and buildings.  Split plating doubling can, however, involve any design element, including peripheral ones.

Another factor involved in split plating doubling is a tendency for the copper plating to catch on the sharp corners of the recesses in the die face.  This can tear open the copper plating as the coin expands.

Split plating doubling has also been referred to as “split-line doubling”, but this term has been largely abandoned.

A dramatic case of split plating doubling is seen above in a 1999 cent that takes the form of an enormously expanded, strongly cupped broadstrike.  A small indent can be seen at 10:00.  The exposed zinc surrounds Lincoln’s bust.  Other areas of exposed zinc are associated with LIBERTY and IN GOD WE TRUST.

This broadstruck 1999(P) Lincoln cent developed split plating doubling in front of Lincoln’s profile. The split plating is indicated by white arrows.

PART X. Wastebasket / Composite Categories:

Ghost Images:

Split Plating Afterimage

Definition: This uncommon effect is restricted to double-struck copper-plated zinc cents.  It is most often associated with off-center uniface strikes and generally is found on the die-struck face.  During a second strike, tensile stresses are magnified along the sharp sides and corners of first-strike design elements.  If the plating is somewhat thinner than normal, it can stretch to the breaking point, exposing the underlying zinc.  The exposed zinc will record the presence of first-strike design elements that have otherwise been obliterated.

This copper-plated zinc cent, struck sometime in the 1980-s, takes the form of a flipover double strike.  The second strike is off-center and uniface (struck against an underlying planchet).  The die-struck obverse face of the second strike displays a split plating afterimage of the reverse design.  The afterimage consists of the letters ERICA and the right side of the Lincoln Memorial

Part V. Planchet Errors:

Upset Mill Errors:

Squeezed-In Debris

Definition: There are numerous entry points inherent in the minting process that allow foreign material to embed itself into a blank, planchet or coin.  A relatively uncommon entry point occurs in the upset mill.  The grooves in the upset mill can trap material that is then transferred to the edge of a blank as it is transformed into a planchet.  There are two major forms of “squeezed-in” debris, discrete pellets and broad, thin sheets of metal.  In the case of the former, small bits of metal or other foreign matter are forced into the edge of the planchet. In the case of the latter, thin sheets of metal — often with a composition strikingly different from the coin itself — wrap around the edge of the planchet, and are eventually struck into one or both faces as well as the coin’s edge.

 Embedded in the edge of this 1968-D cent is a small pellet of non-magnetic, nickel-colored metal.

Embedded in the edge of this 1998-P half dollar is a small piece of ferromagnetic metal (probably steel).

PART VI. Striking Errors:

Collar Deployment Errors:

Stiff Collar Error

Definition: A stiff collar error occurs when an off-center planchet is forced down on top of a collar that is frozen in the “up” position.  This causes severe warping of the coin.  A rounded shoulder is produced on the face struck by the anvil die.  The shoulder ends laterally at a strong collar scar.  A short lip may extend lateral to the collar scar.  On the face struck by the hammer die we generally see the development of a thick vertical flange.

The hammer die can drive a coin completely into a fully deployed collar.  Sometimes the collar is partly deployed.  Sometimes the collar is partly depressed but then freezes in a partly deployed position.

Most stiff collar errors are minor off-center strikes or uncentered broadstrikes.  A few are very far off-center.

The ultimate expression of a stiff collar error is an elliptical strike clip.  Here a planchet is sheared in two between the descending hammer die and the top of the collar (see elliptical strike clip).

Minor horizontal misalignments of the hammer die occur rather frequently in conjunction with stiff collar errors.  The enormous shear forces set up between the hammer die, planchet, and collar tend to nudge the hammer die (or die assembly) in the opposite direction.

In some presses, like the Schuler press, stiff collar errors of varying severity are associated with the majority of minor off-center strikes and uncentered broadstrikes.  Evidently the collar is designed to budge only grudgingly in this press.  Because of this, we might want to refer to this phenomenon as simply a “stiff collar effect” when we’re dealing with issues where the phenomenon is common.

Stiff collar errors are frequently confused with partial collar errors.  They are not the same thing, although the two errors can co-occur.

PART VI. Striking Errors:

Struck Through Errors:

Struck Through Feeder Finger

Definition: A coin struck through a feeder finger will feature a very deep impression, often with vertical walls. The margins of the impression will be concave, straight, or angular.  A sharp angle will often mark the corner of a feeder finger.  The floor of the indentation will usually show a texture distinctly different from that left by a planchet, sometimes smooth, sometimes coarse.  A dark discoloration may be present in the floor of the impression.  Coins are often split or torn apart when struck through a feeder finger.

Note: Several specimens are shown below.

Below is a triple-struck nickel struck through the part of the feeder finger that cradles the planchet. The force of the impact nearly tore off the metal beneath it. It’s tenuously connected to the rest of the coin at one end. The loose flap was telescoped beneath the main part of the coin, probably when the coin was encapsulated.

Double-struck 2006 Isambard Brunell two pounds. This big bi-metallic split & tore as it was struck through a very large, malfunctioning feed finger.

Multi-struck 2007 Malaysian 20 sen struck through feeder finger.

This off-center cent was apparently struck through the side of a feeder finger.  The medial wall of the impression is vertical and the floor is very thin.

Part VI. Striking Errors:

Excessive Striking Pressure:

Stretch Strikes (Die-Struck on Both Faces)

Definition: A stretch strike is an off-center strike with a very wide “slide zone”.  Uniface strikes (coins struck against another planchet) often take the form of a stretch strike because the double thickness greatly increases effective striking pressure.  Stretch strikes are rarer when only one planchet is involved.

A stretch strike that is die-struck on both faces owes its existence to an abnormally small minimum die clearance.  Minimum die clearance refers to the minimum distance between the dies at their closest approach in the absence of a planchet.  A stretch strike can also reflect elevated ram pressure, but this is hard to prove.  Ram pressure is the tonnage delivered to a planchet of normal thickness.  Elevated ram pressure without an accompanying reduction in minimum die clearance will not result in a stretch strike.

In addition to the wide slide zone, a stretch strike will also show exaggerated metal flow in peripheral design elements.

Part V: Planchet Errors:

Pre-strike Damage:

Rockwell test mark in planchet

Definition: A Rockwell hardness tester is used to measure the hardness of metals in the U.S. Mint. It measures the depth of penetration of a steel or diamond-tipped pin relative to the applied force.

When applied to a planchet, the Rockwell test mark will appear as a small circular pit with a smooth floor.  Such planchets are supposed to be discarded. If a planchet with a Rockwell test mark is struck by coinage dies, the pit is not erased. The pit’s original circular outline may, however, be distorted into a slight oval as the coin expands beneath the impact of the dies.

Depicted below is a 1971-S cent with a Rockwell test mark on the reverse face, above and to the right of Lincoln’s statue. This coin falls in with expectations derived from sparse written sources.

This particular example was authenticated by “Lonesome” John Devine and is convincing. The floor of the cup-shaped depression is completely smooth, as would be expected of a dimple produced by a pin tipped by a small steel ball. Although there is no metal flow in the design bordering the crater, there is also no trace of a pressure ridge, indicating that the defect was present before the strike. The pit is oval, rather than circular, but this can be attributed to distortion produced by the strike.