This cannon is believed to be one of the original cannons that were part of the armaments at Fort Frederica on St. Simons Island. This was a key fort, including military and settlers, as the French were establishing their claim to land just north of the Spanish settlement in St. Augustine.
Very cool, looks like a bone or a piece of coral. It reminds me of a graphic novel I just finished called Florida about the French Huguenots' disastrous attempts to settle in Florida. Only available in French though...