The Byzantine period witnessed dramatic changes in its monetary system, not only in the art of coin portraiture, which spread political propaganda and religious ideology, but more so in currency. To maintain the Roman monetary tradition, a new system took shape under Constantine the Great. In AD 309 Constantine established the gold solidus, in weight 4.5g, as the standard currency. The smallest denomination was the nummus, about 7000 to the solidus.

The coinage reform of AD 498 ended the production of the plethora of tiny bronze coins which were in circulation at the time. The new system centered on a follis worth forty of the old, tiny coins. The value was spelled out on the reverse with a Greek numeral M, which was the symbol used for the number 40. Some of the smaller denominations, for example, are the pentanummium, indicated by the Greek numeral E = 5 nummi; the decanummium, I = 10 nummi; and the half-follis, K = 20 nummi. In some instances Roman numerals appear on 40 nummi coins.