|Sestertius (quasi sesquitertius), the sesterce, a coin in value two asses and a half. It was, therefore, one fourth part of the denarius, and the half of the quinarius, and, when the value of the Roman coinage underwent a change, it shared with them a common fate. It was the smallest coin of the Roman silver mint (exclusive of the "pretended libella", which was the tenth part of a denarius, about three farthings of our money). - The sestertius is marked IIS., shewing it to be worth two as and a semis, which multiplied by four make the denarius. - On the well-known medal of Hadrian inscribed RELIQVA VETERA &c. (see this article), as well as on other ancient monuments and in published books, it is written |IIS., namely, with a small line joining together each mark of the as, thus resembling the letter H.
Hoffman, quoted by Rasche, says - "Four sesterces make a denarius, that is ten asses, which, if it is silver, is equal in weight to a drachm."
The sesterce has for its types, on one side a female head helmeted and winged, behind it IIS., on the reverse are the Dioscuri on horseback, and below ROMA. - This little coin is by no means common. Eckhel had seen but two; one belonging to the Cordia family, ascertained to be a sesterce solely by its weight; the other to the Sepullia family, which, besides the right weight, had the mark
The simple sesterce, or little sesterce, says Kolb, was worth about four sous French money (2d. English).
At the epocha when, according to the generally received opinion, silver money was introduced at Rome, viz., in the year 269 before Christ (485th of the city), the monetal unit (l'unité monétaire) was changed; the As, which had become successively of a less important value, ceased to be used in numbering sums. The sesterce was adopted as the monetal unit, probably because this real money (monnaie effective) was the intermedial coin of three established forms of specie.