IDB-1c-1991-01 Interior Die Break

Description

An interior die break occurs when a fragment of die steel separates from the die face entirely away from the rim, and IDB-1c-1991-01 on the 1991 Lincoln Memorial cent documents precisely this phenomenon. Unlike rim cuds, where the break extends inward from the die edge, an interior die break creates an isolated raised area surrounded on all sides by normally struck design — a floating island of featureless metal within the coin's field. This type of break forms when subsurface stress fractures propagate horizontally beneath the die face rather than radiating inward from the rim, eventually undermining a patch of die steel that detaches from the working surface. The separated fragment may remain loosely in place within the die cavity (creating a retained interior die break) or fall away completely, and the distinction between these outcomes produces markedly different appearances on struck coins. For IDB-1c-1991-01, the fragment separated completely, leaving a void in the die that struck coins filled with a raised, design-free mass of metal. Interior die breaks are considerably rarer than rim cuds because most die fractures originate at the structurally vulnerable rim edge. Struck at Philadelphia on copper-plated zinc planchets composed of 97.5% zinc and 2.5% copper, weighing 2.5 grams and measuring 19mm.

External References