I have just come into a real nice Walther PPK.
It is a W series, pre 1940 model in 32 ACP.
The problem is getting the slide off the receiver for cleaning.
I own a number of PA-63's and a modern Interarms PPK/S, so I do know how in theory, to dissassemble them.
With the trigger guard down, and the slide all the way back, I still can not lift it off the receiver.