Part VI. Striking Errors:
Struck Through Die Fill:
Grease Mold Doubling
Definition: A form of raised doubling that develops in association with “grease strikes”. In this form of doubling, die fill of a smooth consistency coats the die surface and fills its recesses. The die fill sets and becomes very stiff as it pounds against many planchets. The layer of die fill escapes from its recess, migrates onto the field, and is struck into a planchet, leaving a raised, slightly enlarged version of the adjacent normal design element.
Grease mold doubling has only been seen in cents dated from 1995 to 1999 and in all cases, only affects the terminal digit.