As (coin)

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The as was a bronze, and later copper, coin used during the Roman Republic and Roman Empire.

The as was introduced in ca. 280 BC as a large cast bronze coin during the Roman Republic, the word as meaning unit or unity. In addition to the as, fractions, the bes (2/3), semis (1/2), quincunx (5/12), triens (1/3), quadrans (1/4), sextans (1/6), uncia (1/12), and semuncia (1/24), and multiples, the dupondius (2), tressis (3), quadrussis (4), quinquessis (5), and decussis (10), of the as were produced. During the Republic, the as featured the bust of Janus on the obverse and the prow of a galley on the reverse. The as was originally produced on the libral and then the reduced libral weight standard. The bronze coinage of the Republic switched from being cast to being struck as the weight decreased. During certain periods no aswere produced at all.

Following the coinage reform of August in 23 BC, the as was struck in reddish pure copper (instead of bronze) and the sestertius (4 asses) and dupondius (2 asses) were produced in a golden-colored alloy of bronze known by numismatists as orichalcum. The as continued to be produced until 3rd century AD. It was the lowest valued coin regularly issued during the Roman Empire, with semis and quadrans being produced infrequently and then not at all by the time of Marcus Aurelius.