Capping. A striking error where a piece does not eject but wraps around the die on subsequent strikes. The resulting piece takes the shape of a bottle cap, hence this name. Collectors call this a cap, or capped die. Mint workers prefer the term cupping.
excerpted with permission from
For Artists, Makers, Collectors and Curators
COMPILED AND WRITTEN BY D. WAYNE JOHNSON
Roger W. Burdette, Editor