Note: This type commemorates the emperor's survival of a near-shipwreck during his return to Rome from the east in the autumn of 176 CE. Neptune stands in the steersman's position, and so is given credit for guiding the ship to safety. On 11th April 2009, Curtis Clay wrote on the Forum Classical Numismatics Discussion Board:

'The evidence for the near shipwreck is the Historia Augusta, Life of Marcus, ch. XXVII:

"After settling affairs in the East he came to Athens and had himself initiated into the Eleusinian Mysteries....Afterwards, when returning to Italy by ship, he encountered a violent storm on the way. Then, upon reaching Italy by way of Brundisium, he donned the toga, and bade his troops do likewise....When he reached Rome he triumphed....Presently he appointed Commodus his colleague in the tribunician power, bestowed largess upon the people, and celebrated marvelous games...."

We know that these events took place at the end of 176 and beginning of 177. Marcus celebrated his triumph at Rome on 23 Dec. 176, and he made Commodus Imperator and TR P so that he too could participate in the triumph. Commodus entered his first consulship on 1 Jan. 177, and the largesse mentioned by the vita, Marcus' seventh, was distributed soon thereafter.

All of the Ship asses are dated to 177, but we can tell from the titles of Commodus, still Caesar but already COS, that they must have been a New Year's issue that was prepared late in 176 for use as good-luck presents on 1 Jan. 177. The ship type, and the emphasis on the good fortune of the two emperors, make it virtually certain that the reference is to the storm that they had survived underway. In the field of Marcus' type we read "To the Good Luck of the Augustus, Father of his Country"; in the field of Commodus' type, "To the Good Luck of the Caesar".'