Part VI. Striking Errors:

Flat-Field Doubling (Imperfectly Aligned Proof

Strikes)

Definition: This form of doubling is restricted to proofs.  It occurs when the hammer die or hammer die assembly shifts position between the two or more strikes necessary to produce a proof coin.  The margins of design elements produced during the first strike are crushed down to the level of the field by the second strike.

Die movement can consist of a lateral shift, a rotation, or a pivot of the die assembly.  Localized FFD is typically found near the periphery of a coin and is likely due to a slight pivot of the die assembly.

Flat field doubling adds a slight premium to the value of a proof.  However, when the flattened design elements are totally separated from their normal raised counterparts, the value increases greatly.  Such errors are usually designated “obverse-only double strikes”, but calling attention to a double strike in a proof coin is redundant, as all proofs are struck at least twice.  I suppose one could call such errors VERY imperfectly aligned proof strikes.

Flat field doubling is closely related to “one-sided” or “obverse-only” double strikes.  The latter is, by definition, restricted to business strikes, as a double strike is part of the error.

The 1962 cent depicted above shows flat-field doubling affecting the date.  For some reason, the crushed portion of the first strike appears slightly incuse in this specimen.

This proof 1985-S cent shows flat field doubling on the date and mintmark.  Photos courtesy of Jason Cuvelier.

Additional photos of the same specimen show FFD on LIBERTY and GOD.

PART IV. Die Errors:

Die Clashes:

Floating Die Clash

Definition: A floating die clash is generated in the aftermath of a die break.  After it breaks off, the die fragment remains behind in the striking chamber and is struck by the dies.  Usually one of the dies is protected by a planchet.  If the other die strikes the working face of the die fragment, the incuse, mirror-image design elements on the fragment are transferred to the intact die (or the intact portion of the broken die).  Those transferred elements are raised and normally-oriented on the die face.  Every coin that is struck afterward has incuse, mirror-image design elements in an unpredictable location.  Most floating die clashes are restricted to the field, as this is the portion of the die face that is most vulnerable to damage.

To see more floating die clashes, click HERE

Part VI. Striking Errors:

Foldover Strikes:

Axial fold

Definition: Due to a misfeed or ejection mishap, a planchet or coin momentarily ends up in a vertical position, and is folded over by the impact of the hammer die.

Schematic illustration of an axial fold. The rectangles represent the hammer and anvil dies respectively. The open circle represents the planchet/coin standing on edge. The thick black horizontal line running across the equator of the circle is the location of the fold.

Part VI. Striking Errors:

Foldover Strikes:

Double foldover strikes (a.k.a., Z-fold)

Definition: Due to a misfeed or ejection mishap, a planchet or coin momentarily ends up in a vertical position, and is folded over by the impact of the hammer die.

 On rare occasions there may be two paraxial folds at opposite ends of the planchet/coin. This would result in a Z fold.

Schematic illustration of a double paraxial fold (“Z-fold”).

PART V. Planchet Errors:

Wrong Planchet and Off-Metal Errors:

Foreign Denomination struck on a U. S. planchet.

Definition: Through most of its history the U.S. Mint has struck coins for other countries.  Occasionally a domestic planchet would pass through a coinage press striking coins for another country.

Foreign denominations can also be struck on domestic planchets when a foreign mint has been contracted to supply planchets to the U.S. Mint.  Canada has occasionally supplied nickel planchets to the U.S. Mint and so we sometimes find Canadian coins struck on these nickel planchets.

The 1970 Philippines 25 sentimos shown above was struck in the U.S. Mint on a domestic cent planchet.  In 1970 the Denver and San Francisco Mints each struck 20 million 25 sentimos coins for the Philippines government.

This coin is in the collection of Jim Zimmerman.

The 1972 Philippines 1 Peso shown above was struck in the U.S. Mint on a domestic clad 50 cent planchet.  In 1972 the Denver Mint struck just under 122 million, 1 Peso coins for the Philippines government.

This coin is in the collection of Jim Zimmerman.

In 2000 the Royal Canadian Mint supplied the U.S. Mint with nickel planchets.  One of these planchets, shown here, passed through a press striking the January, 2000 Canadian Millennium-series quarter dollar.

This coin is in the collection of Jim Zimmerman.

Part VI. Striking Errors:

Foldover Strikes:

Paraxial fold

Definition: Due to a misfeed or ejection mishap, a planchet or coin momentarily ends up in a vertical position, and is folded over by the impact of the hammer die.

Part VI: Striking Errors

Foldover Strikes:

Outward fold

Definition: Due to a misfeed or ejection mishap, a planchet or coin momentarily ends up in a vertical position, and is folded over by the impact of the hammer die.

Part VI: Striking Errors:

Foldover Strikes

 Definition: A foldover strike is a planchet or coin that is folded in half when it is struck on-edge.  The planchet or coin can enter the striking chamber spinning on its edge.  It can be kicked into a vertical position by the feeder finger or ejection arm.  It can roll into the striking chamber on its edge.  Or it can be caught in mid-flight by the descending hammer die.  However it occurs, the planchet or coin is bent in two.

A 1999 cent shows a small paraxial fold embedded in the reverse face.  The margin of the flap is highlighted in black.  The opposite pole shows an edge strike.

PART IV. Die Errors:

Interior Die Breaks: 

Freestanding

Definition: It’s a rare event when a die chip is so large that it warrants being designated an interior die break. Interior die breaks should not be confused with “cuds”. By definition, a cud is a die break that includes the rim and at least a little bit of the field.

Interior die breaks have no direct connection to the rim. They may have an indirect connection via a die crack or split die. Since voids left in the die face by natural fractures span an unbroken size continuum, there is no clear boundary between a “die chip” and an “interior die break”.

Any void encompassing an area of 4 square millimeters or more qualifies as an interior die break. Any void that covers less than 1 square millimeter is a die chip. In between is a gray area. Die chips are commonly encountered in all denominations. In Lincoln cents they include “BIE” errors, “plugged” 5’s and 9’s, and “bugs in the wheat ear”.

Freestanding interior die break on a 1984-P Roosevelt dime. It is situated between Roosevelt’s neck (a long, straight edge), the date, and the mintmark.

1970-D cent with a freestanding interior die break between the base of the Memorial (another straight edge), the rim, and the “O” of ONE.

1987 cent with a freestanding interior die break that extends from the side of the “7” (a gently curved edge) and = almost reaches the rim.