1921 Dated DWM with Unit Marking
 

Any help?

It is found in the two police books, History Writ in Steel and Police lugers;
Schupo Duesseldorf Division(or area or precinct or other) V(five).
First had the 1922 style designation for a sub-area and weapon number cancelled; then just the main designation left with a new weapon number- according to the 1932 regs.

I believe I have accurately paraphrased what Don Maus and Tinker/Gruber wrote in their books.

"Division V" was probably the Schupo Command in Oberhausen. See http://www.historywritinsteel.com/New_Insights.html.