RIDB-1c-1990-01 Retained Interior Die Break

Description

Cataloged with no cross-references to other attribution systems, RIDB-1c-1990-01 on the 1990 Philadelphia Lincoln Memorial cent documents a retained interior die break — a fracture that occurred within the die face away from the rim rather than propagating inward from the edge. Interior die breaks are mechanically distinct from cuds: while cuds form from rim-initiated fractures that separate a wedge-shaped section of die, interior breaks originate from subsurface stress concentrations within the die's interior, such as inclusions in the tool steel, heat treatment inconsistencies, or localized fatigue at sharp design transitions. The fracture creates an isolated island of die material surrounded on all sides by intact die face — a geological analogy would be a sinkhole rather than a cliff collapse. On the struck coin, the broken interior fragment shifts under pressure, producing a raised, roughly circular or irregular area surrounded by normal design detail on all sides. The "retained" designation confirms the broken fragment remained within the die rather than ejecting, continuing to produce coins with the characteristic raised area until the die was retired. Interior die breaks on Lincoln cents tend to form near high-relief design elements — Lincoln's hair, the Memorial columns — where the die steel is thinnest. Struck on copper-plated zinc planchets composed of 97.5% zinc and 2.5% copper, weighing 2.5 grams and measuring 19mm.

Attribution History

• Discovered by Earl M
• Expert attribution by Cuds on Coins

External References