This denarius from the time of the Roman Republic shows on its obverse the head of Roma, the deified personification of the city of Rome. She is wearing a winged attic helmet; behind her is the mark X for 10 as an indication of value.
The denarius was based on Rome's old bronze coin system in which the as was the basic unit. One denarius held 10 bronze asses. Indeed the Latin term 'denarius' literally means 'tenner.'
The reverse depicts the Dioscuri Castor and Pollux galloping into battle in aid of the Romans, their lances ready. Beneath the hooves of their horses is the monogram C. SCR for the moneyer, supposedly Gaius Scribonius.