The key is the epithet symbol of Simon Petrus, the saint patron of the Bremen Cathedral. A single key is also the main element in the coat of arms of the city state of Bremen (see Coat of arms of Bremen) and of the formerly Bremian city of Stade.
The emblematic symbol associated with Simon Petrus, the patron saint of the Bremen Cathedral, features a single key. This same key is also an important element in the coat of arms of the city-state of Bremen (see Coat of arms of Bremen) and the former city of Stade.