Coins pressed together outside the Mint can pass for brockage errors. Here is how bent rims and telltale damage give these fakes away.
Diagnostics of Fake and Genuine Unplated Zinc Cents
in Cents, Planchet errors
How to tell a genuinely unplated zinc cent from one that has been corroded, stripped by reverse electrolysis or re-plated — and the surface clues that give each away.