Thedoublesestertius was a large Roman coin made oforichalcum ("gold-brass") first issued by EmperorTrajan Decius in AD 249–251, as a response to theinflationary pressures of the time which had devalued the buying power of the conventionalsestertius. In reality the new coin was little bigger than the traditionalsestertius, which by then was being manufactured at a lower weight and smaller size than it had originally been, and was not a success. Although commonly described as a "double"sestertius, it was probably worth only onesestertius and a half.[1]
The new coin fell out of use but was revived by the rebel emperorPostumus (259–268), who ruled a breakaway empire consisting of Britain, Gaul and parts of Germany, and was keen to associate his regime with a reformed coinage system. Postumus issued his own version of the doublesestertius, often taking very worn oldsestertii and using these tooverstrike his own portrait and legends on, probably because of a shortage of metal. The doublesestertii were terminated in early 262.[2]
After his reign, the Roman coinage system degenerated further with almost the only circulating pieces being very debased double-denarius coins, known to us asantoniniani or 'radiates' (from the use of theradiate crown). Older coins like thesestertius soon dropped entirely out of use, with many being melted down to create new radiates. By the fourth century AD even these had been discontinued and an entirely new coinage system had been created.