The bust is thought to be of the Roman emperor Caligula. He ruled from 37 to 41 AD. Another view is that it could be an image of his great grandfather, the emperor Augustus. The breast plate has the terrifying face of the Gorgon, Medusa, in the centre. Medusa was a monster with snakes instead of hair, whose face turned people to stone. This image was believed to protect the emperor. This is a copy of a bust now in the Capitoline Museums, Rome; the only significant difference between the two busts is the protective Medusa’s head on the armour.