This is a Roman provincial coin from Thrace, minted in the reign of Augustus. The legend on the obverse is ΒΑΣΙΛΕΩΣ ΡΟΙΜΗΤΑΛΚΟΥ. It shows the head of Rhoemetalces I and his queen Pythodoris. There’s a smaller head to the right of those two. So I would say this coin is RPC volume I, number 1710. Numista doesn’t have a page for this specific type.
There are four examples of this coin type on acsearch.info, but you’d need a premium account to see what they sold for at auction.
