What is the Pope's ring called?

Ring of the Fisherman (Latin: Annulus Piscatoris; Italian: Anello Piscatorio), also known as the Piscatory Ring, is an official part of the regalia worn by the Pope, who is head of the Catholic Church and successor of Saint Peter, who was a fisherman by trade. It used to feature a bas-relief of Peter fishing from a boat, a symbolism derived from the tradition that the apostles were "fishers of men" (Mark 1:17). The Fisherman's Ring is a signet used until 1842 to seal official documents signed by the Pope.

A letter written by Pope Clement IV to his nephew Pietro Grossi in 1265 includes the earliest known mention of the Ring of the Fisherman, which was used for sealing all the pope's private correspondence. Public documents, by contrast, were sealed by stamping a different papal seal onto lead which was attached to the document. Such documents were historically called papal bulls, named after the stamped bulla of lead.