On the Bronze coins of Amisos from the time of Mithridates, I think it likely that the winged bust of a youth is Hermes (Mercury). On the coins of Amisos of this period the obverse and reverse are closely thematically tied one to another (Eros/Quiver, Perseus/harpa or pegasus, Dionysus/Cista Mystica, Athena/Perseus slaying Medusa, Herakles club and quiver, Amazon (?) in a leather persian cap/quiver and un strung bow, Artemis/tripod, etc…).
Hermes gave the Dioscuri their horses and is the bringer of good fortune (i.e. horn of plenty) the literary testimony is slim but solid. Which in turn made me thing about RRC 14/1 and RRC 25/4 in the aes grave series!
Liv Mariah Yarrow 
I like the idea that the bust is Hermes. All of the characters on Mithridates’ coins are connected to the myth of Perseus. Hermes gave Perseus the flying sandals. Perhaps the bust is 15-year-old Mithridates in the guise of Hermes?
I wasn’t aware of the connection between Hermes and the Dioscuri. It makes sense. I had been wondering if the stars on the caps represented the two comets. The first that appeared in the constellation of Pegasus when Mithridates was born and the second that appeared when Mithridates took power in 119 BC. Mithridates saw himself as the bringer of good fortune.