You guys on the east coast have the opportunities to find those old coppers in your back yards. Congrats for swinging your coil over a few nice keepers.I dream of getting into the 1700's club someday...
There we a lot of coppers with the KG3 head on it so I would not fixate on one particular. If it's a worn specimen the 28mm diameter was likely just larger when minted. I don't have any numbers in front of me but I believe Vermont coppers are slightly smaller. KG3 coins are about that diameter.
Try and get the weight, diameter, and a pic of the obv and you'll likely get an ID.
My guess right now is it's a Cartwheel. The last pic shows a big edge.
Steve