PART IV. Die Errors:

Die cracks:

Arcing rim-to-rim die crack (a.k.a., pre-cud) 

Definition:  A die crack that follows a curved trajectory from one point on the rim to another.  The area of the die face cordoned off by such a crack generally amounts to less than 40% of the total area.  The die crack shows only lateral spread.  The presence of either vertical displacement or horizontal offset would indicate the presence of a retained cud.  If the lateral spread exceeds half-a-millimeter, it should be labeled a curved, asymmetrical split die. 

An arcing rim-to-rim die crack may progress to a retained cud, a cud, or an asymmetrical split die.

A prominent pre-cud die crack is present on the reverse of the 1985 cent depicted below. There is no vertical displacement or horizontal offset, so one must assume this area was still attached to the main portion of the die. It also has a large cud in the SE quadrant of the reverse. In addition to that it shows a curved, roughened area of die damage in the NW quadrant caused by a collision between the reverse die and the broken surface of the loose die fragment. That collision might have caused the die to crack in this area.

Below is the reverse of a 1985 cent that shows (1) a large cud in the SE quadrant, (2) a “pre-cud” die crack in the NW quadrant, and (3) a curved, roughened area of die damage in the NW quadrant. The die damage is from a collision between the obverse die and the die fragment that broke away from the SE quadrant.

Close-up of the pre-cud die crack. It could conceivably have worsened to become a cud, a retained cud, or an asymmetrical split die.

PART IV. Die Errors:

Rotated Die Error:

Dynamic Rotation

Definition: In a rotated die error, one of the dies spins around its vertical axis.  In the case of a normal, in-collar rotated die error, it is impossible to determine which die has rotated.  Complex and compound rotated die errors — where the die rotation is combined with at least one other error — do allow us to determine which die rotated.  In the vast majority of cases, the hammer die is the culprit.

Die rotation errors can be stable or dynamic.  This 1945 S Lincoln cent has been found with different degrees of rotation  between the dies making its movement dynamic. It is shown in the images below with a 50° rotation between the obverse to reverse die.

PART VI. Striking Errors:

Design Ablation Error:On Second Strike

Definition: The die-struck design on the surface of a coin is scraped off by lateral (horizontal) die movement.  This can occur on a first or second strike.

This quadruple-struck 2000-D Lincoln cent was struck with inverted dies (reverse die acting as hammer die).  The first strike was normal.  The third and fourth strikes were received in tandem as the coin straddled two adjacent striking chambers (a saddle strike).  The second strike was off-center, uniface, and incorporates a design ablation error.

During the second strike, the impact of the hammer die on the reverse face was relatively weak, even though the aggregate thickness it confronted was doubled by the presence of an an underlying planchet.  After making light contact with the surface of the coin, the hammer die shifted a considerable distance toward 12:00 (reverse clock position).  As the die moved northward, it completely scraped off the first-strike design elements and whatever second strike design elements were generated during the initial impact.  All that is left is a series of fine parallel striations that expose a little bit of the zinc core.

This is the only known example of a design ablation error on the second strike.

Part IV. Die Errors:

Die Damage:

Peripheral Die Damage:

Die Attrition Error

Definition: This is the most recognizable and regular form of peripheral die damage.  A die attrition error is generated when a temporarily misaligned hammer die smacks repeatedly against the beveled entrance of the collar.  This wears away the edge of the field portion of the die and sometimes the entire rim gutter.  This leaves the coin with an unstruck, raised crescent on the face struck by the hammer die.  The internal margin of the crescent is smooth.  Particularly severe die attrition errors can leave peripheral letters significantly truncated.

Die attrition errors are especially abundant among 1983 cents.  A die attrition error
will only be detected after the hammer die has returned to center.

Die attrition errors are sometimes mistaken for cuds (marginal die breaks) and sometimes confused with other, more erratic forms of peripheral die damage and die loss.

The 1991-P quarter shown at upper left displays a severe die attrition error in the northwest quadrant of the obverse face.  The letters of LIBERTY are severely truncated.

The reverse face of a 1998-P quarter is shown at upper right.  The coin was struck with inverted dies (reverse die as hammer die).  The reverse face is nearly encircled by a die attrition error which is visible for about 300 arc degrees.  The attrition is most severe in the northwest quadrant.  The hammer die could have been rotating while it was experiencing a horizontal misalignment in a consistent direction.  It’s also possible that the hammer die (or die assembly) was shifting laterally in many different directions.  When this coin was struck, the hammer die had returned to center but was rotated 140 degrees counterclockwise relative to the obverse face.  The photo shows the orientation of the reverse face when the coin is flipped from left-to-right, with the obverse design oriented north.

Close-up of the word UNITED, where the tops of the letters have been lost.

Close-up showing the words STATES OF. Die loss becomes gradually less severe as you travel around the perimeter.

PART V. Planchet Errors:

Upset Mill Errors:

Coin Struck on a Type I Blank:

Definition: This error type occurs when a blank does not pass through the upset mill and it is struck as a coin. Because it is not rolled and squeezed to a smaller diameter, no proto-rim is generated along the outer margin of the blank.  The edge is also not smoothed out, and instead retains a rough, cut-and-tear texture.

Part V: Planchet Errors:

Wrong planchet and off-metal errors: 

Coins struck on washers, gears, and other hardware

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Definition: Hardware includes washers, nuts, bolts, or machine parts such as malfunctioning feeder fingers.

 Below: A large Bolivian feed finger struck by 1 boliviano dies.

The images below show a 1957-D Lincoln cent that has been struck on a washer. Images courtesy of Heritage Auctions.