Festival of Isis Æ Rome mint

The Isis festival was a major celebration in Rome in the 3rd and 4th centuries, heralding the arrival of the ship of Isis (navigium Isidis) from Alexandria on 5 March. Besides Isis, other members of the Egyptian pantheon appear: Serapis, Horus, Anubis, Harpocrates, and Nilus. Such coins or tokens with imperial busts were first struck by Diocletian at Rome to mark the arrival of the ship, and the tradition continued through the 4th century. The latest imperial bust to appear is that of Valentinian II. Alföldi proposes that in the Middle Ages the festival associated with the Isis ship (also known as carrus navalis) became the car naval or carnival.