Struck Through Grease Question

I'm nto exactly sure what causes this particular problem, but I doubt it's a struck-through issue.

Struck-through means just that. A foreign matter or object comes between the die bearing the design and the blank to become a coin. The die strikes the blank to impart the design onto it, creating a coin, and whatever sits between them mashes into the surface of the coin oblietrating that portion of the design.

The most common struck-throughs are grease mixed with metal shavings, dirt, and other matter. Less common (and usually far more valuable) struck-throughs include but are not limited to staples, thread, string, cloth, feeder fingers, other blanks or planchets (called indents), dropped letters - any number of things that could enter the striking chamber of a minting press.