Error-Ref.com

You are here: Home / Search for "center"

Search Results for: center

Inverted Die Installation

Inverted Die Installation (and how to recognize it)

by Mike Diamond

Throughout most of the U.S. Mint’s history, coins were struck by dies that were set up so that the obverse die functioned as the hammer die and the reverse die functioned as the anvil die. The hammer die delivers the blow, while the anvil die receives the blow, with the planchet sandwiched in between. It is no longer safe to assume that the hammer die is the “top” die and the anvil die is the “bottom” die. Some of the newer presses reportedly operate with the dies oriented horizontally, and Alan Herbert tells me that at least one model of Graebner press first produced in the 1970’s employed a hammer die that thrust upward. At various points in the Mint’s history, the usual pattern of installation was inverted, so that the reverse die functioned as the hammer die and the obverse die functioned as the anvil die (Pilliod, 2000). Buffalo nickels and Mercury dimes were the last 20th century issues to be struck exclusively with inverted dies. It’s not clear why inverted installation was chosen for these and other obsolete issues. After 1945 (the last year in which Mercury dimes were produced), the mint returned to its usual habit of striking coins with a standard die installation (obverse die as hammer die). At least that was the case until the last decade of the 20th century. The status quo was interrupted when Arnold Margolis (1997a, b) reported the discovery of a 1992-D quarter with a reversed partial collar error – a clear indicator of inverted die installation. This was confirmed by personnel of the U.S. Mint after Margolis submitted the coin for examination.

A partial collar error occurs when the collar (the retaining ring that establishes the final diameter of the coin) is not fully deployed during the strike. As a result, part of the coin protrudes above the collar, and it consequently expands beyond its normal diameter in this area. The edge will show a protruding “step” or “flange” that extends out from the face that was positioned above the level of the collar. This face is the one struck by the hammer die, since the collar always surrounds the neck of the anvil die. In coins with reeded edges, the smooth-edged flange will be associated with the face struck by the hammer die, while the thin band of reeding below it will be associated with the face struck by the anvil die. So far, this 1992-D quarter is the only error coin from that year that shows evidence of inverted die installation. It must be understood that it is impossible to determine which die functioned as the hammer die in a normal coin. The presence of inverted dies is only revealed when it is accompanied by certain kinds of errors. It must also be appreciated that inverted die installation itself is not an error, just an alternative setup that is fully intentional. I am not aware of any error coins from 1993 or 1995 that show evidence of inverted dies. I have one 1994-D dime with a reversed partial collar, so this tells us that the practice may have persisted throughout this period, albeit at a nearly undetectable level. In 1996, the practice of striking coins with inverted dies accelerated. A small number of nickels and dimes with inverted partial collars are known from this year, along with a 1996-D broadstruck quarter with a faint trace of reeding next to the obverse face (see below). All these early examples are from the Denver Mint. By 1997, error coins struck by inverted dies can be found in all denominations from cents to quarters, although they are still quite scarce. 1998 shows a conspicuous increase in the number of error coins struck with inverted dies, and the frequency of such coins seems to grow in each subsequent year. Since 2000, it appears that nearly all state quarters have been struck with inverted dies. Other denominations continue to be struck with both normal and inverted die setups, although today the inverted setup may actually dominate. It is unclear why the minted started tinkering with inverted die installation in 1992, why it remained so uncommon for the next three or four years, and why its frequency has increased steadily since 1998. It does appear that inverted die installation has some connection with some of the newer-style presses, (e.g., Schuler and Graebner), that have been installed in recent years.

Recognizing Inverted Dies

 

Only certain types of errors will betray the presence of inverted dies. Below is a list of errors that supply reliable clues about die installation.

 

Partial
collar

We have already mentioned the partial collar error. Figure 1 shows a 1996-D dime with partial collar error that was struck with inverted dies. As you can see, the obverse face has a normal diameter while the reverse face is wider than normal. An oblique view shows the narrow band of reeding next to the obverse face and the smooth flange that projects beyond it.

Off-center
strikes

Most off-center strikes and some uncentered broadstrikes show a collar scar on the face struck by the anvil die. The collar scar is produced when the part of the misfed planchet that protrudes outside the striking chamber is forced down upon the top of the collar and depresses it. The collar floats on springs in the older style Bliss press and we may

presume that functionally similar arrangements exist in other press models. Figure 2 shows an off-center 2000-P nickel with a strong collar scar on the obverse. The unstruck part of the planchet is also slightly cupped up toward the reverse, another indicator of inverted die installation. While not all off-center strikes show cupping, its presence is a reliable indicator as to which die functioned as the hammer die. Cupping in a simple off-center strike (both faces die-struck) is always toward the hammer die.

Ram strikes

It is often assumed that all off-center strikes are struck out-of-collar. However, a small percentage are forced completely into a collar that is frozen in the “up” position. I have termed these errors “ram strikes” (Diamond, 2000, 2001). Ram strikes are very distinctive in appearance and are characterized by a total of 9 diagnostic features. Among the most distinctive of these features is the presence of a rounded shoulder on the face struck by the anvil die and a vertical flange on the face struck by the hammer die. Ram strikes go back to at least 1928, the date shown on a Mercury dime with this error (Diamond, 2001). However, I have seen at least one Indian cent with what looked like a ram strike, so it may extend back even farther. All the ram strikes that I have encountered dated1997 or later were struck with inverted dies. Ram strikes dated 1996 or earlier all seem to have been struck with a conventional die arrangement (with the exception of Mercury dimes). Figure 3 shows a 1998 quarter with a ram strike that was struck by inverted dies.

Broadstrikes

Simple broadstrikes – both centered and uncentered –may expand horizontally or may show cupping. Cupping, when present, is always toward the hammer die. Figure 4 shows a 1999 cent with very large uncentered broadstrike that was struck by inverted dies. Cupping is well developed and is directed toward the reverse die, which clearly functioned as the hammer die.

Another way that broadstrikes can provide clues about die installation is if there happens to be a trace of reeding (or some other sign of contact with the working face of the collar) somewhere along the edge. Whichever face the reeding trace is associated with is the face that was struck by the anvil die. Figure 5 shows a broadstruck 1996-D quarter with a trace of reeding next to the obverse face.

 

In-collar indents and partial brockages

Although indents and partial brockages that are struck out-of-collar do not provide reliable clues about die installation, those that are struck within the collar do. In-collar indents and partial brockages must be located on the face struck by the hammer die. If a coin or planchet is inserted between the coin and the anvil die, the coin has to be a broadstrike, since the collar must be located beneath both coins.

When a planchet or coin is struck into another planchet that remains seated in the collar, the metal beneath the intrusive coin is subjected to increased effective striking pressure. This often forces the metal to squeeze over the top of the collar, beneath the intrusive coin. The resulting “lip” will extend out from the face struck by the hammer die.

I have not yet seen any in-collar indents or partial brockages struck by inverted dies, but any such coin should be instantly recognizable.

 

Horizontal misalignments (in-collar)

Horizontal misalignments of the hammer die should also provide useful clues about die installation, provided that the coin is struck in-collar. In a major misalignment, the hammer die forces the collar down to the level of the coin, and this often produces a narrow “lip” along the edge. Whichever face is associated with this lip will be the one struck by the hammer die.

Major horizontal misalignments can confidently be assigned to the hammer die, provided that the coin is struck in-collar. Lateral movement of the hammer die is not constrained by a surrounding collar. Likewise, because the collar surrounds the neck of the anvil die, any horizontal displacement of the latter would require displacement of the former and the production of a broadstrike. In the past it was considered safe to assume that any major horizontal misalignment had to be affecting the hammer die, regardless of whether the coin was struck in or out of the collar. The collar was not thought to be capable of any significant horizontal movement. However, this assumption is no longer valid as it appears that some of the newer presses are permitting major horizontal misalignments of the anvil die together with the collar.

 

Collar Clash

Collar clash occurs when the hammer die collides with the top of the collar or scrapes along the working face of the collar. Such an accident leaves an impression inside the rim gutter of the die or at the junction between the rim gutter and the die neck. In denominations with reeded edges, collar clash takes the form of serrations located at the top of the rim.  The presence of collar clash on the reverse rim is a strong (but not infallible) indicator that the reverse die was employed as the hammer die.

On rare occasions collar clash will be found on the face struck by the anvil die or even on both faces of the same coin. Since the anvil die is surrounded by the collar, it’s clear that the anvil die would not have struck the collar from below. It might be caused by the anvil die scraping continuously along the working face of the collar. It also might be caused by a sudden sideways movement of the hammer die or the collar that is violent enough to leave marks at the edge of the rim gutter.

 

Summary

Inverted die installation in contemporary issues started at least as early as 1992, but only rose to detectable levels in 1996. By 1998, this die setup became relatively common and today seems to be at least as common as the conventional mode of die installation.

Inverted die installation can only be detected when it occurs in conjunction with certain error types. These include partial collars, off-center strikes, ram strikes, broadstrikes, and indents and partial brockages that are struck in-collar.

 

Addendum

In May, 2004, at the Central States Numismatic Society’s annual show, I stopped at a bourse table manned by James Essence and Len Roosmalen. In their case I saw a saddle strike on a previously struck 1996cent. I was surprised to see that the coin was struck with inverted dies. The area between the two off-center strikes bulged conspicuously toward the reverse die and the obverse face of each off-center strike was uniface (struck against a blank planchet) while the reverse was die-struck. Together, these features provide compelling evidence that the obverse die functioned as the anvil die in this press. This is the earliest recent cent I’ve come across struck with an inverted die set-up (although I’ve seen nickels, dimes, and quarters that date to this year or before). It also provides proof that inverted set-ups were at least occasionally used in dual or quad presses.

 

References

Diamond,
Mike (2000) The ram strike. Errorscope, Nov/Dec 2000

Diamond,
Mike (2001) Ram strike update. Errorscope, March/April 2001

Margolis,
Arnold (1997a) Help wanted for possible new error. Error Trends Coin Magazine,
February 1997, page 29

Margolis,

Arnold (1997b) What we used to know may not be so today! Error Trends Coin
Magazine, December 1997, page 29

Pilliod,
Chris (2000) A heads up. Errorscope, Nov/Dec 2000, page 6

 

Invisible Strikes

PART VI. Striking Errors:

Weak Strikes:

Invisible Strike

Definition: Invisible strike errors result from a failure to maintain proper minimum die clearance. Minimum die clearance is the closest approach the dies make in the absence of a planchet. It is a pre-set safety margin that prevents the dies from clashing. Normal minimum die clearance is greater than zero but considerably less than the thickness of a planchet. This serves to prevent die clash while insuring a strong strike.

Once in awhile, the dies fall out of adjustment or something prevents them from approximating normally so that minimum die clearance exceeds the thickness of a planchet. Any planchet that enters the striking chamber during such a malfunction leaves the same way it came in – featureless. However, if another planchet, coin, or foreign object intrudes into the striking chamber, it takes up the excess space between the dies. This permits a die-struck design to be generated on the opposite face, directly across from the indent, partial brockage, or strike-through error created by the intrusive object.

Below are images of a Presidential dollar with an invisible strike. The obverse face shows a 25% partial brockage of the reverse design that consists of a shallow rim impression and an incuse, mirror-image version of Liberty’s torch flame.

The die-struck design on the reverse face is weakly struck and takes up an equivalent 25% of that face.

Coin courtesy Fred Weinberg

This dime features an indent on the obverse face. Right across from it on the reverse face is an area of die-struck design. The rest of the planchet is unstruck. The dies were too far apart at their closest approach to leave an impression on the portion of the planchet lying beyond the indent. The intrusive planchet took up the excess space between the dies, permitting the reverse (anvil) die to leave a strong imprint.

The half dollar has a 30% indent on the second strike in conjunction with an invisible strike. The first strike shows a little bit of weakness here and there.

Irregular Planchet: Heavier Than Normal

PART V. Planchet Errors:

Irregular Planchets:

Scraps / Fragments:

Heavier Than Normal Coin of the Same

Denomination:

Definition: This type error occurs when a coin is struck on a planchet that has been incorrect rolled to an oversized thickness by the rolling mill.

The 1941-P Lincoln cent was struck on thicker than normal stock and weighs 4.1 grams. The normal weight for this coin is 3.1 grams.

Images are courtesy of Heritage Auctions.

Irregular Planchet Off Metal

PART V. Planchet Errors:

Irregular Planchets:

Scraps / Fragments:

Off-metal

Definition: Occasionally fragments of metal are struck that have a composition different from the coin whose design it carries.  Sometimes the composition of these fragments matches those of another denomination.  In other cases the composition is quite exotic.

This undated Roosevelt dime has been struck on a piece of copper scrap metal.

Images are courtesy of Heritage Auctions.

Irregular Collar Break

Part IV. Die Errors:

Collar Cuds:

Irregular Collar Break

Definition: Many collar breaks take the form of an irregular bite extending from the upper edge of the working face of the collar.

Many collar breaks take the form of an irregular bite extending from the upper edge of the working face.

This 1989-P nickel has a large, irregular collar break that extends from 10:00 to 1:00 (obverse clock position).

Low angle view of the collar break.

The lowest
tip of the break’s advance falls just shy of the reverse rim (image below).

Irregular Planchet: Feeder Finger Material

PART V. Planchet Errors:

Irregular Planchets:

Scraps / Fragments:

Feeder Finger Material

 

Definition: This error occurs when a coin is struck on fragments of a broken feeder finger.  Sometimes the feeder finger is intact when struck, and is fragmented by the strike.

This 2000-P Sacagawea dollar was struck multiple times on a feeder finger.


Images are courtesy of Heritage Auctions.

This 2007-D Roosevelt dime was struck three times on a feeder finger fragment.

Images are courtesy of Heritage Auctions

 

 

Irregular Shaped Cuds

PART IV. Die Errors:

Die Breaks:

Irregular Cuds

Definition: When an irregular chunk breaks off the corner of a die, it leaves an irregular cud on the coin.  A cud with a ragged internal border can develop gradually or instantaneously.

The images above show an irregular die break on a 1987(P) Lincoln cent.

Images are courtesy of Heritage Auctions.

Irregular Straight Clips

PART V. Planchet Errors:

Blanking or Cutting Errors:

Straight Clips:

Irregular Straight Clips:

Definition: A blank or planchet that has been punched from the end of the of the strip. Though most clips from this position are completely straight, some have irregularities and are not completely straight.

The 1973-D Jefferson nickel presumably had its planchet punched from the end of the strip. The irregular rim indicates that it made its way through the upset mill after being through theriddler. While the edge is slightly curved, it would not fit the description of a curved clip.

Images are courtesy of Heritage Auction

Isolated Machine Doubling

PART VI. Striking Errors

Machine Doubling:

Isolated Machine Doubling

Definition: Isolated machine doubling affects only a small portion of an area without affecting the surrounding features.  This affect is most often encountered on the mintmark, since the mintmark is often fractionally higher than surrounding features and thus more vulnerable to impact the retreating die.

The image above shows a 2000-P Sacagawea dollar with isolated machine doubling affecting the P-mintmark.

The 1946-D Roosevelt dime shown above has its mintmark subjected to machine doubling. None of the surrounding design elements show this  doubling affect. Notice that the mintmark has two shelf like steps indicating that this may have been caused by a chattering die.

Janvier Reduction Lathe

The Janvier Reduction Lathe was used to reduce the images that were found on the galvano transferring them onto the master die.

The large white disc at the center of this Janvier Reduction Lathe is a galvano for the 1999-S proof Kennedy half
dollars.  The device near the bottom of the galvano is tracing out the design in that area.

Here we see the Master Hub for the 1999-S proof Kennedy half dollars that is being carved in the same Janvier Reduction Lathe as seen in the previous photo.  The device at the bottom of the Master Hub is doing the engraving.

Images and text courtesy of John Wexler. To learn more concerning the Janvier reduction lathe, click HERE