It may have been formed from a cut and shear burr on the planchet as the copper seems to lay over the top of the edge. It kind of looks like a lamination and probably feels like you could peel it off.
It shouldn't scrape off with a fingernail or such. It is a stretched edge of a blank that is folded over onto the face of the planchet in the upsetting mill. Usually cause by a dull blanking dye that stretches the copper past the edge, just as the nickel is stretched over the copper in the blanking die. Edge photo of a quarter planchet.
