Overstrike, Overstruck. A coin or medal struck on an already existing coin or medal (the existing piece is used for a planchet instead of a blank planchet). A flattened outline of the features of the first, called the undertype, will often be seen beneath the second, called the overtype. Overstrikes lack the sharp image of a piece struck on an ordinary blank with a uniformly smooth surface which normally fills all die cavities. An overstrike may fill some cavities and not others leaving an imperfectly struck piece.

In addition the undertype will appear in mashed or foldover design; lines indicate where relief or letter once existed. Not all of the relief or lettering of the undertype will be discernible because there is distortion in the surface movement of metal as it flows toward the die cavities of the second die. These lines are more visible in the fields, less so in detail or lettering. Identifying the undertype – also called a as a host coin or medal – is always a challenge for the numismatist and quite satisfying when this identification can be made with any degree of certainty.

In some instances overstriking is done by caprice – by intentionally placing a struck piece in a press; in other instances it is a coining error where, for example, a piece from a previous run was left in a hopper or tote box, filled with correct blanks and then fed into a coining press where the fugitive piece is struck a second time. A third instance is a coinage run where all blanks are previously struck pieces.

The first to do extensive overstriking were the Byzantines, about 1000 A.D. Instead of melting old coins, rolling and blanking new planchets, old coins were struck as is, producing unsightly new coins.

At the Philadelphia Mint misstruck large cents circa 1795 were rolled thinner, blanked for half cent size and struck with half cent dies. Despite going through these three operations some evidence of the prior detail can be detected as albeit, considerably obliterated. Breen called these .

Overstrikes differ from counterstamps. A counterstamp has one or more punches impress lettering or design leaving intact most of the original design. An overstrike is a second die completely obliterating the original design.

References:

N8 {1969} Laing, p 39.

NE42 {1982} Doty, p 242-243.