One thing is certain, it is not an 06 frame, it is a frame without a safety, yet without provision for the shoulder stock. The frame was not made by Mauser and strawing of small parts is present. If the gun is still rust blued, which is easy to verify, a refinish is unlikely but not impossible. The gun is in .30 Luger, a calibre that was mostly used in the early years, pre-1908, and after the treaty of Versailles.

From a look at the photos I think a refinish that would erase all markings has not taken place but without a close look at it, it is just speculation.

Fact is, that Walther in Ulm made Walther PP in post-war Germany without serial numbers on either frame or slide. I have seen one personally.