Hairline. The narrowest and earliest form of diebreak; as the width of a hair. Hairline diecracks tend to "grow" – to lengthen, widen and deepen on successively struck pieces as the break progresses in the die. See broken die. The finest engraved line of a hand engraver is also called hairline; an example would be the minimum width line in script lettering. A fine pointed graver is used to make such a cut with a minimum depth.Collectors sometimes call fine line scratches on the surface of a numismatic item hairline scratches.
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