Hard for me to tell without the rest of it, and unfortunately, I don't know the size of that coin... there were plain brass shoe buckles and it kind of looks like one, if it's indeed curved.... but it could also be just some other kind of buckle.
In my opinion, most likely part of a shoe buckle, yes. Now age? I have no idea. With that said, my "W.A.G." would be mid-1700s Cool find from across the pond!