The reverse shows Jupiter standing left, holding a scepter in his left hand, he also has a chlamys hanging over his left arm. In his right hand he holds a Victory on a globe (called a Victoriola which is a carved cult statue of victory which is holding out a wreath). There's a palm leaf at Jupiter's right foot. Jupiter presents the victoriola, which symbolizes the gift of victory in battle from the gods and the renown that came with the victory, to the young Caesar. The legend reads PROVIDENTIAE CAESS which translates as "The foresight of the Caesars". The second S in CAESS means that there are two legitimate heirs to the throne, in this case Licinius II and Crispus. For a bit more on Providentia see here. There is a over a Δ in the right field.