Shelly,
This pistol is a real puzzle to me. Bottom line is that I really don't know but note the following:
1. There was a unit mark on the front grip strap before the P.L.II.50. was stamped. This mark was ground off but traces remain. It appears that this earlier mark ended with II.5?. I'm guessing that the "?" was a "0", the same weapon number as the replacement mark.
2. I think the mark on the heel (butt?) of the grip strap is P.II.10.50." and that the cancellation marks create the appearance of an H. It could be either but the prevalence of II in these marks makes me lean this way. Maybe a close examination by you could resolve this. Typically, the cross bar in the H is narrower than the vertical strokes.
3. Based on my research into police school marks, I am tempted to say that the grips strap mark P.L.II.50. represents the Polizeischule für Leibesübungen (Physical Education) as I ecstatically did for your C96 holster but these marks make me wonder about both cases. I don't really know what they did at this school, but I don't imagine they needed many weapons. Finding two examples in two days stretches my belief in the Good Fairy of Lugerland.
4. It's not really clear in what order these marks were made. Clearly, the ground-off mark on the front grip strap preceded the one that was lined out. However, where the heel mark fits in the sequence is unclear. I have the impression that this location was used very early in the 1920s, before the 1922 orders specified the marking location on the front of the strap. If so, this may have been the original mark, which was canceled and replaced by the ground-off mark (perhaps to conform to the 1922 orders) and subsequently replaced with the current mark on the front of the strap which was ultimately canceled, itself. The apparent maintenance of the II (unless the heel mark is an H) and the weapon number makes me feel that the gun stayed within the Command represented by II throughout all this. However, if this is true, I really don't understand the difference between the P. on the heel mark and the P.L. on the front strap.
5. Finally, the lack of sear or mag safeties indicate the gun was not in police service following issuance of the 1933 orders mandating them. It says nothing about its earlier life. I do believe the unit marks are Prussian police and the fact that they are all canceled means it was removed from police service some time prior to 1933.
Now, wasn't all this a big help?
P.S. What's the s/n of this pistol?