Starting in the 4th century A.D., Rome issued a series of coins that was clearly pagan. Maybe, as Andreas Alföldi thought, this may have been an attempt by the pagan aristocracy of Rome to use the old religion of mystery and romance to confront the pro-Christian policies of Constantine. Roman emperors performed vota pvblica, or public vows, on the third of January. Somehow, an Egyptian ritual involving ships of Isis, navigium Isidis, became associated with the vows of the emperor. This became the Festival of Isis, and Romans celebrated it on the fifth of March. Rome issued coins with the bust of the current emperor and a reverse with Egyptian deities like Isis, Serapis, Anubis, or Harpocrates. Constantine must surely have disliked his image on a coin with pagan gods, but the citizens of Rome really enjoyed their festival, and Constantine knew he had to judiciously pick his battles. By A.D. 380, circumstances had changed, and the emperor Theodosius passed laws forbidding the use of the imperial bust on this pagan coinage.
Mint personnel circumvented these laws by changing the bust of the emperor into a deity, for example an image of Theodosius would be changed only by putting on the headdress of the god Serapis. People celebrated the Festival of Isis as the celebration of a new year, and they used a carrus navalis, or ship on wheels. Alföldi even theorized that in the Middle Ages, the Church may have interpreted the phrase carrus navalis as carne vale, which may have been the beginning of the modern carnival. However it is generally agreed that carnevale translates roughly as “going without meat.†The citizens of Denmark still hold a carrus navalis celebration.
A good reference for these coins is Coinage and History of the Roman Empire by David Vagi, but I didn’t see the reverse and obverse of the coin below paired together in Vagi, but the same type is illustrated in A Dictionary of Roman Coins by Stevenson
Festival of Isis
4th cent A.D.
ISIS FARIA; draped bust of Isis right.
VOTA PVBLICA; Isis in galley, supporting sail.
