A caduceus is a staff, often winged, with two snakes wrapped around it forming a figure eight with the top end open. It was a heralds staff associated with Mercury who was the messenger of the gods and the god of commerce. It was originally a simple staff with two white ribbons attached giving authority and inviolability to the herald who carried it. In mythology it was said that the caduceus originally belonged to Apollo but that he exchanged it with Mercury for his invention the lyre. Mercury used the caduceus to guide the souls of the dead to the underworld. He also could control the living and the dead with it, or turn anything it touched to gold. In later mythology the serpents were added to the staff when Mercury used it to seperate two fighting snakes who then became entwined around the staff thus making it a symbol of peace and concord.

A caduceus on a denarius of Nero and a caduceus held by Felicitas on a Antoninius of Gordian III

The Roman caduceator was a herald who was sent to treat for peace however as his symbol he carried sacred herbs torn up by their roots from within the inclosure of the Capitol, instead of a caduceus, which was not in use amongst the Romans as the symbol of a herald. On coins the caduceus is usually depicted as a symbol of Mercury or Felicitas and symbolises commerce, peace and prosperity.