Medusa is not the only creature in Greek mythology with snakes for hair. The monstrous dog Cerberus, who fought Herakles, had a mane of snakes.
There is an animal with snakes in its mane on a very rare Greek coin. This diobol (weight 1.08g, 11mm diameter) seems to depict an animal with a mane of snakes on the reverse. The animal has whiskers and triangular ears. The coin is rare; I have only been able to locate two other examples.
I suspect that this coin reverse depicts the head of Cerberus. In addition to the snakes, the ears resemble the ears of Cerberus on vase paintings. Some dogs have whiskers, and some Greek and Roman art shows Cerberus with a at least one lion head. Thus, none of the features rules out Cerebus. In addition, Cerberus is not always depicted with multiple heads.
The reverse is thus not a generic panther or lion as suggested by the catalogers of the coin example, but a rare depiction of Cerebus with a mane of snakes.