As (coin)

The As is a small copper ancient Roman coin valued at 1/4 of a sestertius and 1/16 of a denarius. It was the smallest denomination in common circulation during the Roman Empire.

Although often only slightly smaller than the dupondius, which is valued at 2 to the sestertius, the as is worth half as much. This is due to the composition of each coin; the dupondius was made of a golden bronze alloy while the as was made of reddish copper. The dupondius usually featured the emperor wearing a radiate crown, indicating that it was worth twice as much as the as.