Both are on horseback; the god is giving the diadem to the king.
According to the 14th Roman ordo, of 1241, the pope places on the emperor's head first the mitra clericalis, then the imperial diadem.
In some cases it would appear as if the diadem studded with pearls had been worn, and in others something more of the character of a crown.
He witnessed the chequered career of Stilicho as actual, though not titular, emperor of the West; he saw the hosts of Radagaisus rolled back from Italy, only to sweep over Gaul and Spain; the defeats and triumphs of Alaric; the three sieges and final sack of Rome, followed by the marvellous recovery of the city; Heraclian's vast armament dissipated; and the fall of seven pretenders to the Western diadem.
In fact, Lewis the Meek never actually " wore the diadem of France " either, being the Holy Roman Emperor.