On the prow of the ship above stands an ass, or donkey. I found the nature of this coin as an ass as rather amusing, but looking at it in hand, something struck me. It’s hard to capture it in a photo, and my own effort above is rather poor. But the ass has a rather striking attribute, shall we say. He is what we demurely call ithyphallic. A clearer example can be seen, by those who are not faint-hearted, here.
Grueber, in his 1910 catalogue of the coins of the British Museum, does not tackle this aspect of the imagery directly. He tentatively suggests that the coin may be linked with M. Julius Silanus on the grounds that this is the “ass of Silenus, the companion of Bacchus”. Silenus is often depicted, lolling fat and drunken, on an ass; and sufficiently often on an ithyphallic ass too, that the suggestion is not iconographically impossible. But the imagery is not something that needs to be complicated too far: donkeys are perceived as lustful in modern society as well as ancient, and the addition of his tumescence is natural to him.
It reminds you how different ancient society was, though; I can’t imaging getting an image like that in my change today.