Anomaly. Deviation from the normal. In striking this is a piece differing from a proper business strike, a striking or mint error, a wrong or defective planchet, an off center or double struck piece, or any other error piece. In casting this is s blister or gas pocket. In patina work this is a water stain, fishtail, or wipe mark; in acid etching a foul bite. Every process has its blunders or malformations, an anomaly is that which is different from the acceptable. Anomalous effects after a coin or medal is issued includes any damage, mishandling, graffiti, or such.
excerpted with permission from
An Encyclopedia of Coin and Medal Technology
For Artists, Makers, Collectors and Curators
COMPILED AND WRITTEN BY D. WAYNE JOHNSON
Roger W. Burdette, Editor