What's this Bison? Hi, what causes this. Copper wash, weird alloy mix, or what? I've seen these on ebay and never paid them much mind because artificial toning is so easy. I found this in a bank roll so I know the color is not artificial. One forth of this bison is copper colored. The photo does not do this coin justice. Kinda cool. Thanks in advance.
On the left 1/4 of the coin (bison's butt) there is a copper color. This is not a reflection. Very noticable to the the naked eye. It's hard to photograph, looks much better seeing it in person.
If genuine, it could be "copper wash" or some other form of mint discoloration. Problem is, nobody really understands the sources of copper staining or even thick layers of added copper that sometimes appear on nickels and clad coins. It's a vexing problem, but not an uncommon one. It's possible that prolonged immersion in a chemical rinse bath preferentially liberates copper atoms from the core and outer clad layers of clad coins (or from solid Cu-Ni coins) and then these atoms are re-deposited later as the solution becomes saturated. It's one guess among many and none fully explain the full range of variation seen in these errors.
Thanks Mike, I'm new to this forum and you sound like a good source for error coin information, which is what I mainly collect. Yes this coin is genuine,it stood right out, came out of a bank roll from a 50 roll box I got from my bank. The coin appears copper in the affected area. So this is an error and its called copper wash. I'm not selling it ( I collect errors) but wouldn't this carry a premium being a Bison and all?
The affected area is small and the copper color is not that strong. So the premium would be slight, in my opinion.
I'm new to this forum and could be off base. But I believe another possibility is that the coin could also be missing part of its clad layering. Although I can't decipher form your photo, I have seen other coins where partial clad layer was missing. A quick way to check is to weigh the coin and compare the weight to a "normal" one. If it truly missing some clad layer. It would be lighter.
Nickels are composed of a solid 75% copper / 25 % nickel alloy. Since it doesn't have a clad composition, it cannot be missing a clad layer.
