Today I came across a 2013 D Mount Rushmore that seems to be an error. The head side looks to be stamped good, the only thing that I can see is a very slight ring just inside the text all the way around the quarter. It isn't stamped into it, it looks more like a bluing or darkening of the metal. On the back is where I believe is the error. It has a copper ring around the very edge, no lip on the egde, and looks to be almost blank except for the center where you can barely make out a nose and silhouette of washingtons face. The coin seems to be slightly dished. Its almost as if something was pushing up on the middle of the face side when it was stamped and only part of the stamping transferred. I looked online and couldn't find anything like this and it looks too clean to have been done by hand. Hopefully someone on here can help me figure out if this is an error? Thank you to everyone.