Definition of "follis"

In Italy, the exarchs at Ravenna preserved the denominational structure of the currency, striking the bronze folles along with fractions and three silver denominations marked as pieces of 125, 150, and 500 nummiae (pl. 23.200). The solidus was officially exchanged at 300 folles (= 12,000 nummiae) or the rate that had obtained under Theodoric.

1996, Kenneth W. Harl, Coinage in the Roman Economy, 300 b.c. to a.d. 700, Baltimore, Md., London: The Johns Hopkins University Press, page 199

In the beginning, Antioch followed the weight policy of Constantinopolitan coins, but after a break in minting in 540/541–541/542 caused by the sack of the city by the Persians, the mint of Antioch continued to issue bronze folles of high weight standard, ever if the weight in Constantinople was already reduced by that period.

2016, Pavla Drápelová, “Province in Contrast to City: Irregularities and Peculiarities in the Coinage of Antioch (518–565)”, in Nicholas S. M. Matheou, Theofili Kampianaki, Lorenzo M. Bondioli, editors, From Constantinople to the Frontier: The City and the Cities, Leiden: Brill, part 4 (The Cities), page 180

The silver miliarensia from that era were minted exclusively for propaganda purposes, and in smaller amounts than the gold coins (nomismas) and the copper alloy coins (folles). They were practically not used in circulation, although in theory twelve miliarensia were equal in value to a gold nomisma.

2022, Vladimir Penchev, “What the coins from the Preslav treasure can tell us about the social status of its owner”, in Contributions to Bulgarian Archaeology, volume XII, page 70