I picked this one up at a very good price. The seller didn't know what the marking was.
Finish is well worn due to the nature of the unit. Militarized police were used in conjunction with Reichswehr on the Polish and Czech frontiers during the Weimar era to defend Germany's Eastern border.
"Grenzpolizei" {Frontier / Border Police} units were interspersed with the Army units to fill the gaps on the borders. Subsequently these pistols saw a lot of use. Grenzpolizei were often mounted units. The pistols spent long durations bouncing around in their holsters. Kind of rough on the blue.
The magazine also has a faint "G. P. 1" stamped on the base.
Ron