As (Roman coin)

The following fractions of the as were also produced: the bes (2⁄3), semis (1⁄2), quincunx (5⁄12), triens (1⁄3), quadrans (1⁄4), sextans (1⁄6), uncia (1⁄12, also a common weight unit), and semuncia (1⁄24), as well as multiples of the as, the dupondius (2), sestertius (21⁄2), and tressis (3).

After the as had been issued as a cast coin for about seventy years, and its weight had been reduced in several stages, a sextantal as was introduced (meaning that it weighed one-sixth of a pound).

It was the lowest valued coin regularly issued during the Roman Empire, with semis and quadrans being produced infrequently, and then not at all sometime after the reign of Marcus Aurelius.

[3] The as, under its Greek name assarion, was re-established by the Emperor Andronikos II Palaiologos (r. 1282–1328) and minted in great quantities in the first half of the 14th century.

3–4 grams and forming the lowest denomination of contemporary Byzantine coinage, being exchanged at 1:768 to the gold hyperpyron.