Someone beat that one with an ugly stick. As the little dog said when he sat on the sandpaper "Ruff."
Welcome to Coin Talk. You now have a very interesting coin to show at parties and make up stories about it. It is a PMD quarter for sure.
Soaking in Nitric or hydrochloric acid does wonders. Used to do this in the college chem lab and then spent them (although you have to take them out before they get as thin as yours).
Just something for you to think about. If it were a Quarter struck on a Copper Cent Planchet then it would be the same size and thickness of a normal Cent. I know you didn't say that it looks like it was struck on a Cent but sometimes other members think that it's what they have. I agree to acid damage.
Looks like someone put it on the railroad track and flattened it. It looks somewhat bigger around then the comparison coin beside it. It may have been pounded flat with a hammer or similar tool. People find all kinds of damaged coins from people doing things to them for who knows what ? It might be worth 25 cents ,but not anymore . Welcome to coin talk . Dillan