The original gold medallion (multiple of 9 solidus), Mint of Trier, resides permanently in the Louvre and is depicted and described by Askew (The Coinage of Roman Britain, # 580, page 54). The Reverse is especially interesting as it depicts the personification or genius of London (?) in front of the Tower supplicating before Constantius I (Chlorus) who is on horseback with a Roman galley full of soldiers in the Thames (?) in the background. The reverse legend REDDITOR LVCIS AETERNAE (restorer of eternal light) alludes to the restoration of Britain to the Roman Empire by Constantius after his victory over the usurper Allectus in AD 296.
This, and four other similar gold medallions, was part of the famous Arras hoard discovered in 1922.
James


