As

The as (plural: asses) was the base-unit bronze denomination of the Roman monetary system, with origins in the heavy cast bronze bars (aes grave) of the early Republic. Originally weighing a full Roman pound (approximately 324 grams), the as was progressively reduced through a series of weight reforms until it reached about 11 grams under Augustus — a fraction of its original weight but still a substantial bronze coin of 25–28mm diameter. The as was worth one quarter of a sestertius and one sixteenth of a denarius, serving as the standard small-change coin of the Roman world. Imperial asses feature the emperor's portrait with a bare or laureate head (the radiate crown was reserved for the dupondius, the next denomination up). Like sestertii, asses bear the SC mark indicating senatorial authority over base metal coinage. The denomination was struck at Rome and occasionally at provincial mints through the third century. Asses are less commonly collected than denarii or sestertii, partly because bronze is more susceptible to corrosion and fine examples are harder to find. Well-preserved asses with clear legends and smooth patina are valued by specialists. Notable series include the Augustan commemorative asses, the Britannia asses of Hadrian, and the large-module first-century issues.