Error coin post 1: What type of error is this?

This is part of a three coin set, from the mint with an error on the middle issue. What type of error is this, the discoloration is in the shape of a coin, but I am not sure how this would have got there.
The discoloration looks to be part of the metal, at least at 10x magnification.
Ideas?
The discoloration looks to be part of the metal, at least at 10x magnification.
Ideas?
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I would suggest asking Mike Byers of www.mikebyers.com, or even Dog97, a member of this forum.
Except if that's what it was, the copper should be in a crescent shape, with the area protected by another SBA blank remaining brilliant.
So I don't have a clue. Interesting coin!
Hope this helps some. Of course you will want other opinions.
Capped Bust Half Series
Capped Bust Half Dime Series
But I'm not sure how copper wash could explain it either. Maybe one blank got some contaminated wash water on it, and later rested on another blank, and the contaminated water then formed the coin shaped pattern? I dunno... not sure there'd be enough copper in just a little contaminated water.
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