Likely a vest button of European heritage. Colonial to post-Colonial period. Seemingly pewter or similar pot metal. I've seen that type/look button while hunting in Canada, where French buttons were common. Rhode Island's heavy connection to the French dates back to the early 1500s.
Nice job in hearing that small find. If you can find that sized reading you'll surely find that nearby 1 reale, half dime or the likes. Minelabs are famous for precision hunting.