NNP

Hard Goldplate.  An enhanced goldplating by the addition of a small amount of other metal in the process of goldplating. It is used on jewelry for extending the wearing qualities; and was developed at the beginning of the 20th century by Tiffany & Co., in addition to other jewelry companies. The items may be marked HGP.  See heavy goldplate, electroplating.

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