This is a George II Half Penny. Coins worn like this are often excavated from early British sites in North America. The British were poor colonial masters when it came to supplying coinage to their American colonies. The only reliable source of non-Spanish coins came from the pay that British soldiers stationed in America received, and these coins were almost always half pennies. Because of the chronic shortage of coins they stayed in circulation for decades until worn smooth like yours.
Roderick