NNP

Boundary.  The line between the contrasting metals of the core and the clad metal in a clad composition. These lines are only observed on the edge of a sandwich metal coin although they may become distorted during striking. They are quite obvious when the two metals are of differing color. Should the outer layer separate from the core, debondiong; it occurs at the boundary (where one metal separates from the other). This term was first used in 1970 by numismatic writer Walter Breen.

References:                                                                                                                              

C60 {1970} Breen.

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