I found this 2012d dime in a roll it came from an OBW roll of 2012d dimes I opened at work. This was the only one in the roll like it and I have since 2012 opened or looked through about $2000 a week in dimes.
I do not think it is an error. It looks like the plating was chemically stripped from the one side. If it was a mint error, the heads side would have mint luster.
The back of the coin looks normal and all of the coins that were in the roll appeared normal as well. How would the coin have mint luster if it was missing the clad layer that makes them shine? I don't much about the minting process of coins.
It's the high pressure of the stamping process that creates the mint luster or cartwheel effect when you rotate the coin between your thumb and forefinger. Therefore, any metal, whether plated or not, would show mint luster if it came into contact with the dies. Also, a chemical stripping (or even cleaning at that) dulls the metal.
I just read your original post and you mentioned you found the coin in an OBW. If the coin came from the mint like that, I would suspect a plating error. However, it only occurring on one side and the lack of mint luster still makes me think the coin endured some kind of post mint process.
