John,
Look a bit harder at the unit mark. I'll bet the E is really an S. If so, this mark indicates weapon #881 of the Schutzpolizei (larger city uniformed police) of Command II in the Prussian district of Schleswig in the province of Schleswig-Holstein. Based on my recent research, I believe Command II was the city of Kiel.
Photos of this holster and its markings would be a great help in identifying it further.
|