There is a fairly common coin from the FEL TEMP series with a galley reverse. RIC VIII mentions that this type might allude to a visit that Constans made to Britain. RIC gives the Konrad Kraft article "Die Taten der Kaiser Constans und Constantius II" as a reference. Though RIC usually gives the date of issue circa A.D. 348- 350, Kraft argues for an earlier issue probably around 344.
The reason that this issue seems to allude to a visit to Britain is because there are several ancient sources that reference this trip to Britain. The real significance, according to the sources, was that it was made in the winter...a very dangerous time to make this crossing. Libanius has more about the weather which I did not include. This probably happened A.D. 342- 343.
Firmicus Maternus,
De errore profanum religionum On the Error of Pagan Religions Chapter 28:6
“You (Constans) have overthrown your enemies, enlarged the Empire, and, to add greater luster to your exploits, altering and scorning the fixed order of the seasons you have done in the winter what was never done before or will be again: you have trodden upon the swollen and raging waters of the Ocean. The wave of a sea already become almost unknown to us has trembled beneath your oars, and the Briton has quailed before the unexpected visage of the Emperor.”
Libanius Oration LIX: Panegyric of Constantius and Constans
137 “It is not right to pass over in silence his voyage to the island of Britain, because many are ignorant about the island.”
141 “If therefore after the island had rebelled, its inhabitants were holding an uprising, and the empire was being plundered, the news had arrived, and he had been seized with rage on hearing it and had thrown the die for the voyage, to report his act of daring would not have been to the credit of his resolve, but the crisis deriving from the rebels would have taken away the greater part of the glory.”
Translation from
From Constantine to Julian: Pagan and Byzantine Views A Source History.
Ammianus Marcellinus,
Res Gestae Book XX.1
“But in Britain in the tenth consulship of Constantius and the third of Julian raids of the savage tribes of the Scots and the Picts, who had broken the peace that had been agreed upon, were laying waste the regions near the frontiers, so that fear seized the provincials, wearied as they were by a mass of past calamities. And Julian, who was passing the winter in Paris and was distracted amid many cares, was afraid to go to the aid of those across the sea, as Constans once did (as I have told).”
https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Ammian/20*.htmlThe trip to Britain is even commemorated on a medallion (RIC VIII Rome 338), known from a single example with a reverse of BONONIA OCEANEN. The reverse legend is what the Romans called the city Boulogne-sur-Mer, often just called Boulogne; which was the place the expedition to Britain was launched from. There is even a law in the Theodosian Code issed by Constans from the city in January 343; which gives weight to A.D. 342- 343 for the date of the expedition, since there would be no other reason for Constans to be in Bononia Oceanen.
https://catalogue.bnf.fr/ark:/12148/cb44974338hfor corroboration of the A.D. 342- 343 date, see A Dictionary of Roman Coins
"Light is thrown on the date of this expedition from the subscription of the Lex V of the Codex Theodosius (lib xi lit 16), viz. "data viii Kal Febr Bononiae, Placido et Romulo Coss." These men having entered their consulship AD 343. [Most of the above remarks, cited by Eckhel, are in Ducange, Dissrt. de Num. inf. aevi sect 28]"
https://www.forumancientcoins.com/numiswiki/view.asp?key=BONONIA%20OCEANEN
