DDR markings
 

Yesterday I acquired an interesting E.German rework of a 1938 dated S/42 PO8. On the left frame rail, just above the grip, I can see traces of the letters "PMP" and am curious as to what type unit this may have been. Had the marking been "MP" I would have guested Marinen Polizei, but I'm stumped by the preceding "P". Could this be a city or a distrit? Any assistance would be appreciated. TH