Go here, http://p38forum.com/
Go to the PP & PPK forum. There, go to PP & PPK Postwar. There is a thread there entitled Feg copy of Walther PPK or something like that. Go to the post by Mr. Dieter H. Marschall.
Herrn Marschall is most probably the ultimate authority on Walthers. You can go to the bank with what he says.
Or have your friend write to Walther Germany. Or to Earl.