Ring of the Fisherman cardinal. Ring of the Fisherman The 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
Noncommutative ring is isomorphic to a product of finitely many "n"-by-"n" matrix rings over division rings "D", for some integers "n", both of which are uniquely determined up to permutation of the index "i". In particular, any simple left or right Artinian ring is isomorphic to an "n"-by-"n" matrix ring over a division ring "D", where both "n" and "D" are uniquely determined. As a direct corollary, the Artin–Wedderburn theorem implies that every simple ring that is finite-dimensional over a division ring (a simple algebra) is a matrix ring. This is Joseph Wedderburn's original result. Emil Artin later generalized it to the