came across this one a while ago and didn’t think anything of it until I happened accross an article about a black nickel dubbed the “black beauty”. Could this be something similar?
The one on the right is just dirty. The one on the left... I'm no expert, but... it doesn't look like an "improperly annealed" coin. Wait for the real professionals to chime in ;-) Welcome to CoinTalk!
Right on, thanks. Left coin is just for comparison. I did take just a wet wash rag to the black one and attempt to wipe it off but it didn’t really remove anything
Don't bother doing that.. It is Environmental Damage. Once the Copper in the Clad layer which contains Cupro Nickel darkens it stays that way. Not a Mint Error.