In a Whitman book of Jefferson's I got at an auction, the guy had a couple of miscellaneous error coins on the last page. There was a lamination flaw, a clipped planchet, and two 1960-D Bar 0's. Then there was this one. At first I thought it had something to do with the dark stain on it, as the dark portion looked like it might have been struck through something. But looking some more I think he probably kept it for the odd rim on the coin. It seems to have a step on it. Is this an error, or PMD like what you see when you remove a penny from those "Keep Me And Never Go Broke" tokens?
They have been stacked and been in the sun, or in a heated area, as a annulling process. Also in or on newspapers. Printing ink can turn a coin as such.
Place another nickel at the edge of the stain. It will match perfectly. The shiny portion was protected by the coin on top while the exposed side toned to due whatever reasons.
