Decentius, Caesar, 350/1-353. Half Follis (Bronze, 15 mm, 2.28 g, 12 h), Rome, spring 351-352. MAG DECENTI-VS NOB CAES Bare-headed and cuirassed bust of Decentius to right. Rev. VOTA PVBLICA Nilus reclining left, with reeds in his hair, leaning on urn from which water flows, holding ship in his right hand and reed in his left. Bastien 506. RIC 478. Extremely rare. Very minor smoothing, otherwise, good extremely fine.
This charming piece belongs to a larger group of coins related to the Ploiaphesia or Navigium Isidis, a festival held on March 5 in honor of Isis, the great patroness of sailors, which coincided with the opening of the shipping season in early spring. Despite the rise of Christianity in the 4th century, the festival remained in vogue, and the related coins show a rich variety of designs connected to Egypt such as Isis herself, Serapis, Anubis, Harpokrates or, as on our coin, Nilus. Indeed, these fascinating pieces are some of the last truly pagan coins struck by the Romans, although it has been theorized that the festival lived on as Christian Carnival. Most of the coins show either Isis or Serapis on the obverse, but some extremely rare pieces such as ours do actually portray the Roman emperor.