Wiktionary
n. A large bronze or (rarely) small silver coin minted during the Rome and Empire, valued at two and a half as.
Wikipedia
The sestertius, or sesterce, (pl. sestertii or sesterces) was an ancient Roman coin. During the Roman Republic it was a small, silver coin issued only on rare occasions. During the Roman Empire it was a large brass coin.
The name sestertius means "two and one half", referring to its nominal value of two and a half asses, a value that was useful for commerce because it was one quarter of a denarius, a coin worth ten asses. The name is derived from semis, "half" and "tertius", "third", in which "third" refers to the third as: the sestertius was worth two full asses and half of a third.
English-language sources routinely use the original Latin form sestertius, plural sestertii; but older literature frequently uses sesterce, plural sesterces, terce being the English equivalent of tertius. A modern shorthand for values in sestertii is IIS (Unicode ????), in which the Roman numeral II is followed by S for semis, and the whole struck through; but because this symbol and striking through letters are not always convenient, HS may be used instead, with the horizontal bar of the 'H' representing the strike through the numeral II, rather than the letter H.
Usage examples of "sestertius".
Though the denarius was a more common coin in circulation than the sestertius, Roman accounting procedures were always expressed in sesterces.
I ask you, Brutus, what does Rome have provinces for, if not to let Romans make a sestertius or two out of them?
Suppose you find your friend to-night, and place to his order sestertii in such amount as you choose.
I offered publicly in the market-place five thousand sestertii for a living cock and hen, but was told that the race had long since been exterminated, and that, as money would no longer buy food, money was no longer desired by the poorest beggar in Rome.
Wherefore, in the same spirit I say, can I get them to run together, moved by my will, the four as one, thou shalt have the sestertii and the crown, and I my revenge.