Bishop's Ring with the Symbols of the Four Evangelists

The cast and chased ring is rectangular at the top and decorated on the four sides with the symbols of the four Evangelists: the angel (John), the winged ox (Luke), the eagle (Matthew), and the lion (Mark). On the narrowing on both sides, an eagle and two crossed keys are depicted, each decorated with three red stones. On the round side of the ring, an inscription has been applied, which is largely worn away: PA . . . IS (?). The rectangular (gem) stone, which was set in the ring, is missing.