The this denarius was issued in 51 BC by Servius Sulpicius (SER SVLP). It depicts the head of the Greek god Apollo.
The maritime trophy on the reverse alludes to a naval victory. On the prow of a ship stands a mast with an anchor and a rudder hanging from its crossbar. On top sits an aplustrium, the fan-shaped decoration from the stern of Roman ship. The figure on the left of the trophy is a prisoner.
Apollo on the obverse refers to the island of Delos, where he was born, as Greek legend had it. In the year 69 BC Apollo's sanctuary there was destroyed by a pirate attack. Some years later the Roman commander Gnaeus Pompeius Magnus defeated the pirates and was honored with a memorial on Delos.
Perhaps it was this victory that the issuer of the denarius wanted to celebrate.