I see a bust looking right in pictures 1 and 3, but the chin seems sharper than KGIII's and the head seems smaller and closer to the top of the coin than on the KGIII's. The neck seems strangely straight up and down and long.
I spent about 15 min looking at other images but I don't see a good match - but I'm no expert.
I look forward to an expert chiming in.
As DCMatt said, if you could tell us the diameter in millimeters it would help. Or at least picture your coin with a known coin like a US penny or dime.