Hi folks,
Standard .32 ACP (7.65mm) PP magazines will fit a standard PPK, prewar, postwar or mixed, but will stick out the bottom. Obviously, PPK magazines won't work in a PP.
PPK/S .380 magazines will not fit into a .32 ACP pistol or into a pre-war .380 (9mm Kurz) pistol.
There were a small number of PPs and PPKs made with a heel type mag catch. Magazines for these have no cutout for the standard catch. They can use standard mags (without the finger rest), but not vice versa.
Jim