Definition: As the name implies, an “acid damage” is a coin that has been immersed in a corrosive solution, most likely a strong acid.
The diagnostics of an acid damaged coin include:
1. A diameter smaller than normal.
2. Perfect centering of the design.
3. Uniformly mushy design on both faces.
4. Thin or absent design rim.
5. Lack of metal flow in design elements bordering the coin’s edge.
The surface may or may not show an unusual texture.
Through the years of searching Lincoln cents, some have turned out to be plated. The images below show various plated Lincoln cents that have been plated with different types of metal. Why and who would conduct this plating is not known, but it does seem to be still occurring.
Coins Struck By Counterfeit Dies
Definition: This category includes 1) counterfeit designs struck on counterfeit planchets, 2) counterfeit designs struck on genuine planchets, and counterfeit designs struck over genuine designs.
Amateurish efforts often involve the use of relatively soft dies. (This should not to be confused with abnormally soft, but entirely genuine dies that can result from improper annealing, quenching, and tempering.) A soft die can be made by squeezing a coin into an unstruck planchet (or other metal disc), and then affixing the disc to a metal rod.
Genuine coins struck a second time by soft counterfeit dies show soft, blended overlap between the original, genuine design and the counterfeit second design.
Solder on Coins
The appearance of a coins surface can be altered by the addition of solder. Where it is to alter the appearance of a design element or to add an independent feature (die crack and such), it can be accomplished to a degree where it may fool the average collector.
Squeeze job (vise job, sandwich job, hammer job)
Definition -These terms are used in reference to coins with an incuse design impressed into the surface. Such alterations are designed to mimic a brockage or a double strike.
Un-plated Lincoln Cents
Definition: A Lincoln cent struck on a zinc planchet that was never plated with copper. This type of plating error coincides with the introduction of copper-plated zinc cents in 1982.
This error type is frequently duplicated outside the mint by either plating a normal cent with zinc (or another white metal) or chemically stripping the copper plating from a normal cent.