Found this yesterday in Savannah, GA folded in half and believe it to be a Continental Navy Officers Button from the American Revolution (would have been crimped to wood or bone). I was using the XP Deus HF Elliptical Coil. Thanks for looking.
A little update on this button, we had our monthly Coastal Empire MD Club Meeting last night and talked to some guys that have found these buttons in the Savannah area over the years. The button is most likely a US Rev War Continental Navy Officers button made by the French for the US specifically.