Different SNs

Hi everyone, new to the forum, but not to Walthers. I just bought a 7.65 Manurhin PP with the a fairly well done defacement of the Walther name on the slide. I've read about the reasons for that, so that isn't my question.

I did read that these pistols often have the SN electropencilled inside the slide, and when I looked mine has a different SN, although in the same date range (221XX on the frame). Anyone have an idea where this might have been used previously?

I have read they might have been police weapons, and this looks a lot like it was carried a lot and shot a little. There's some slight wear on the front of the frame behind the trigger guard pivot, and a bit more on the butt by the mainspring, like it was weathered being carried in a holster somewhere.

Thanks in advance.