I just wanted to let you know, never use anything acidic, such as vinegar, or lemon juice, for I will destroy any remaining detail on the coin, lemon juice or vinegar may make non-dug copper coins look shiny, but I will just destroy non-dug coins. Anyways, Good Luck on IDing you coin, and accurate diameter and/or weight will help narrow it down.
I'm guessing it's a colonial copper, most likely a King George Halfpenny
Large Cent 1796-1834: Weight: 10.89 grams Diameter: 29mm
Large Cent 1835-1857: Weight: 10.89 grams Diameter: 27.5mm
King George II Halfpenny: Weight: 9.37 grams Diameter: 28.2mm
King George II Halfpenny's Weights vary from 8.61-9.37 grams
King George I Halfpenny: Weight: Same as King George II, Diameter: 27.8 grams (note: distinctive rim, and high relief design)
King George III Halfpenny: Same as King George II half penny
King George I Halfpenny:

King George II Halfpenny:

King George III Halfpenny:
Thanks, Coinman123