My 1920

[Mac Cat]

I looked through Sam Castanzo's "World of Lugers", which is a rich collection of stamps and came up with

#16 1920-1921 DWM and ERFURT Weimar military police receiver proof. (shown below)

The stamps on your luger are pretty hard to make out while I think the eagle is right, the letters on the bottom don't seem to match up as much.

This is my own opinion and I'm not any kind of expert on reworks or police lugers.