Macedonian Kingdom, Antigonos Gonatas, Athena with Counter-mark, 329-277 BC
Con/ F; brown patina, but it's the CM that is important here.
Obv/ Head of Athena r., in crested Corinthian helmet with helmet counter-mark
Rev/ Pan advancing r., erecting a trophy; B-A in upper field, ANTI monogram below Pan.
Ref/ Greek Sear 6786 var