It looks hand-cut and shaped whatever it is.
Its thicker than normal copper sheeting.. Maybe it's just left over from cutting a hole in something else..not sure.
There's Native American history in the area the first thing that actually went through my mind was that it was some piece of copper traded to the natives.. that they made something out of but that might be just fanciful thinking it doesn't quite have the patina to be that old I don't think.
Thanks man.