A denarius serratus, one of the serrated denarii of the time of the Roman Republic. The coin shows the usual images of the early denarii: on the obverse the head of Roma, the goddess and personification of Rome, wearing a winged Attic helmet; behind her is the mark X for the value of 10 asses. The reverse depicts the Dioscuri Castor and Pollux, galloping into battle in the aid of the Romans, their lances ready. Beneath the hooves of their horses a wheel as mint control mark.