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Made about 1935
You will have to contact Walther
Early 1940s
No such serial number in the PPK/S range.
Might be listed in Dieter H Marschall's book.
Dieter Marschall's book might have some information. If not, try the p38forum.com
Impossible to answer without the serial number.
1938
You will need to contact Walther to find out.
The PPK/s is a PP with a PPK slide.
1931 to date
You need to find a copy of Dieter Marschall's book on Walther handguns.
Someone over on the P38forum.com, in the PPK sub forum, might have access to the sn data.