Royal headgear

This is a traditional representation of Jupiter (naked, bearded, and holding a thunderbolt), but the god is also wearing a crown of leaves. Since the Hellenistic period (3rd-Ist century BC), this object had symbolised royal power: it was worn by the kings who succeeded Alexander the Great and shared his empire in Greece and around the Eastern Mediterranean.
During the Roman period, the crown of leaves was mainly worn by the military leaders who returned in triumph to Rome. It was therefore a royal symbol or a sign of victory, which corresponds exactly to the image conveyed by Jupiter, the king of the gods.