I dug this today and I believe it’s a coin of some type. There is lettering around the edge on one side and what looks like a bust in the center. There is nothing identifiable on the other side. The letters look like part of the word states?
In times of small change shortage flat buttons did enter circulation - that may be why this button was possibly altered and the shank smoothed over. Someone wanted to turn it into a "coin" that could pass.