The Origin and Early History of the Follis
One of the mosaics of the villa at Piazza Armerina, which are generally dated to the early fourth century A.D., depicts in connection with a contest a table on and under which are what are evidently prizes, crowns, palms, and bags labelled , that is 12,500 denarii. I suggest that these bags are the folks, which were at this date and later units of currency. A follis was, as its name implies and as various metrological writers confirm, a purse, and these purses, according to literary and epigraphic sources, contained bronze coins or denarii. The follis is first attested in 308–9, but was probably introduced at an earlier date, somewhere between the great debasement of the antoninianus by Gallienus and the reform of the coinage by Diocletian, when the antoninianus or Aurelian's piece marked XXI were the only coins in circulation and their value had sunk so low that some higher denomination was essential. If this is so, the coins which the follis contained cannot have been denarii, which had ceased to be minted, though the value of the follis was reckoned in denarii.