As (Roman coin)
The (plural ), occasionally assarius (plural assarii, rendered into Greek as , assarion) was a bronze, and later copper, coin used during the Roman Republic and Roman Empire. Republican era coinage. The Romans replaced the usage of Greek coins, first by bronze ingots, then by disks known as the aes rude. The system thus named "as" was introduced in ca. 280 BC as a large cast bronze coin during the Roman Republic. The following fractions of the were also produced: the (), (), (), (), (), (), (, also a common weight unit), and (), as well as multiples of the "as", the (2), (2), and [tressis  reference needed]. After the "as" had been issued as a cast coin for about seventy years, and its weight had been reduced in several stages, a "as" was introduced (meaning that it weighed one-sixth of a pound). At about the same time a silver coin, the denarius, was also introduced. Earlier Roman silver coins had been struck on the Greek weight standards that facilitated their use in southern Italy and across the Adriatic, but all Roman coins were now on a Roman weight standard. The denarius, or 'tenner', was at first tariffed at ten "asses", but in about 140  BC it was retariffed at sixteen "asses". This is said to have been a result of financing the Punic Wars. 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. As the weight decreased, the bronze coinage of the Republic switched from being cast to being struck. During certain periods, no "as"ses were produced at all. Imperial era coinage. Following the coinage reform of Augustus in 23 BC, the as was struck in  reddish pure copper (instead of bronze), and the or 'two-and-a-halfer' (originally 2.5 asses, but now four asses) and the (2 asses) were produced in a golden-colored alloy of bronze known by numismatists as . The as continued to be produced until the 3rd century AD. It was the lowest valued coin regularly issued during the Roman Empire, with semis and being produced infrequently, and then not at all sometime after the reign of Marcus Aurelius. The last as seems to have been produced by Aurelian between 270 and 275 and at the beginning of the reign of  Diocletian. Byzantine coinage. 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. It was a low-quality flat copper coin, weighing ca. 3–4 grams and forming the lowest denomination of contemporary Byzantine coinage, being exchanged at 1:768 to the gold "hyperpyron". It appears that the designs on the "assarion" changed annually, hence they display great variations. The "assarion" was replaced in 1367 by two other copper denominations, the "tournesion" and the "follaro".