NNP

Master Pattern.  A working copy of a coin or medal model, in hard material from which hubs or dies will be made. A master pattern in metal is made from the artist’s original model (usually plaster) – it must be the exact same diameter as the model with the same height of relief. After the original model has been edited, all final touchup completed on the model, and all approvals obtained, the plaster bas-relief model is then cast into some permanent hard form. This can be a foundry cast in bronze or other metal, or more often, an electrogalvanic cast in copper. The later would be a galvano that would be either positive (being a hubshell) or negative (being a dieshell). If a less permanent form is required it can be made of epoxy.

This master pattern then could be used to make one or more hubs or dies by pantographic reduction; a hub would be cut from a hubshell, or a die from a dieshell. The master pattern would then be sent to storage should it be needed for cutting hubs or dies in the future. The advantage of the master pattern is that any number of hubs or dies can be made from it, and, of course, in several sizes if so required. Also it provides a permanent repository of the original three-dimensional design. There are instances of a century old electrogalvanic pattern being used to make a new medallic item on its centennial. The British term is former.  See electroform, electroforming.

 

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