Police Erfurt with matching holster but mismatched bbl/receiver

[RShaw]

I see a "PA" above the first digits "42" on the base of the mag if I don't expand that photo too much. An "L" I can't make out myself. Are there any other possibilities?
This rig as a whole is more interesting than just a mismatched pistol and lose accessories. Therefore it's more of a collector. Unique in its own way I think