I found the comments section the most interesting. Not to be derogatory, but many of those posting had little knowledge of PP pistols. I did find the video interesting,if not so short for the Forgotten Weapons site. It was a prototype, but probably was early in the war as Walthers was churning out PPs and P.38s later. Still a good example of what could have been.
I would rather say that this "KPK"-prototype was made by the end of the PPK production as it shows some features of the very late production PPKs - such as the "PP-type" rear sight, the absence of the milled step in the frame (at the axle of the trigger guard) and black grips.
Dieter H. Marschall.