Introduction

A coin can be damaged in a million different ways while in circulation, without being present when the damage is taking place, you don't really know the true cause or the intent. There are a number of tell-tale signs of specific damage though, which once you see it you can pattern match in your brain similarities. Some important points to remember:

Corrosion

Copper-Plated Zinc Cents

Zinc-Plated Steel

Copper-Nickel-Plated Copper

Copper-Nickel Alloy

Silver-Copper Clad

Silver-Copper Alloy

Tooling

Coin Rolling Machine

Snips or Shears

Mounting - Bezels

Antique Coin Savers

Alterations

Elemental

Captured

Foreign Substance

Copper-Plated Zinc Cents

Lincoln cents made from late 1982 to now have a zinc core and are plated with a thin layer of copper. Minting errors, as well as damage, may leave the zinc exposed and a layer of hydrozincite is formed over the exposed area. As a coin circulates, this protective layer is removed and forms again, repeated exposure, reaction, removal lead to the increase of the affected area, until eventually, the coin may no longer be recognizable as a coin.