Letter I

Golden Glossary of Coin Terminology

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Impaired Proof

A proof which has numerous hairlines or has been mishandled or abused.


Sunk below neighboring surfaces (intaglio). Gold Indian Quarter Eagles and Half Eagles (1908-1929) are the only U.S. coins that feature an incuse design.

Indian Head Cent

U.S. copper coin (1859-1909). Common name for the Longacre design of cent.


A bar of metal used for the production of coins.


A desirable form of toning on a silver or nickel coin. Iridescent toning covers virtually all of the coin’s surface, while still permitting the coin’s natural luster to shine through with its full intensity. Some numismatists feel that in order for toning to be called iridescent, it must have all the colors of the rainbow, or at the very least, most of them.