Constantine the Great began minting the solidus in 312 CE and used it to replace the aureus as the official imperial gold coin. Valentinian II continued to mint these coins during his reign (375-392 CE). The reverse legend emphasizes the harmony of the three ruling Augusti, Valentinian II and his uncle Valens and half-brother Gratian. In fact, Valentinian's proclamation occurred when he was just four years old and had been highly irregular. This led to tension between him and his co-rulers, tension which this sort of image was engineered to mask. Andrew Carroll 2011.