Tough one. What size is it in mm?
It looks similar to a young head George II bust, but if you notice there's an S at the 1 O'clock position. That rules out a British regal Halfpenny or Farthing (genuine) coin, and several Colonials I can think of off the top of my head. If it's something like an Evasion (counterfeit) halfpenny, it would be hard to get a match because there's so many... but even suggesting it could be that is a complete shot in the dark, and not many are found in North America anyway. If I were you I'd first look at all the American possibilities that have a left facing bust, because if it's not American the chances get pretty slim you'll ID it.
