File Cut. An acceptable form of test cut, whereby the lightest possible cut is made on the edge of a medallic or numismatic item to reveal the base metal and whether the piece has been plated. Ideally a small scratch is made in the most inconspicuous place to remove only the plated layer if one existed. Any removal of base metal is considered damaging to the test specimen and lowers its numismatic value. Gold items can be tested with nitric acid in the exposed area, or it can be examined under high power magnification to ascertain the color, and thus the composition, of the base metal. Colors of base metals are listed under bleeding.Generally file cuts should only be performed by professionals, amateurs tend to remove more metal than necessary and damage the piece being tested. In cataloging coins and medals file cuts and test cuts should always be noted. In theory only one such file cut needs to be made, however, the author has observcd two on one object, as if the first was not accepted for an inspection of the under metal, and a second was required.
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