If its circa 20mm then its probably an English 17th C Token (Farthing). If so it will be near impossible to track down the full attribution, as you need at least the place or person & all you really have is whats in the centre & that initial will be the first letter of the Maker or his Wife, so it really doesn't help enough.
Congratulations Calabash ! Hope it will get some consideration for banner. Anytime you dig a coin that old in the Coastal Carolinas area you know you have something special.