Is this an error or just damaged? On the reverse the legend and the denomination appears to be overlapping the rim. The edge is mostly copper and flat .
it's not an error. When you were a kid did you ever sit on a curb and take a quarter and scrap it against the concrete curb. Thus sanding down the edge? amongst maybe a bunch of other methods of it being smoothed down ... The "real" question is "how in the minting process" can this occur? If the collar wasn't in the machine, then the coin would get smooshed out which would look completely different. The quarter has the rim upset on one side, and a lot of the reverse .. which the upsetting process which does both at the same time. etc etc
