"It's an Irish Militia Button , a unit that never served in America. However, it was common practice to draft men from the militia into the regular regiments¬ (the militia basically formed a reserve pool of recruits for the regular army) ¬ which is possibly how it arrived here in the US. Since nearly every British regiment had a good number of Irishman in it , unless you found specific data regarding men from this unit being drafted into a particular regiment , it's anyone's guess. There were a load of British/Irish militia units and their buttons are occasionally found here in the US. ¬ ¬ "
Don has a large collection of rev war and CW relics - he buys rarer items and if anyone here sells than saves and wants to possibly try and sell to him
hear he pays good - I can give you his contact