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2002 P COPPER DIME
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It's possible that is an improper annealing error. These used to be referred to as "copper wash" or "sintered plating". Under high and/or prolonged heat in the annealing oven, Cu-Ni clad and solid Cu-Ni coins sometimes develop a layer of copper on the surface. The precise mechanism remains obscure. Do copper atoms migrate to the surface? Do nickel atoms migrate away from the surface, leaving the copper fraction behind? Are nickel atoms liberted from the surface? Are copper atoms liberated, only to be re-deposited as a pure layer? None of the above?
Your photo is not large enough and doesn't have enough resolution to determine whether it is, in fact, an improper annealing error. There are other causes of a coppery color -- chemical staining, plating, etc.Mike Diamond. Error coin writer and researcher.
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