I remember exactly that in the original frame of the P38k there was only one recoil spring, even though the 9mm Luger barrel and not the 30 Luger barrel was installed when I bought it. That was probably also intended by Walther because of the originally planned sale in 30 Luger in Italy.
I don't have a P38k but I do have a P4 which is the gun that it's based off of as well as P38's in 9mm Luger, 7.65 Luger, and .22LR and a P5 9mm. All of mine came with two springs installed.
According to the P38 schematics that I have, all three calibers use dual recoil springs (druckfeder). The 9mm uses one part number but the 7.65 and .22 share a second part number. The slide of the P38 .22 will only engage and compress ONE of the two springs. The second spring is basically insurance in case someone puts a centerfire upper on that frame.
Maybe someone was trying to cure function problems in your P38k by screwing around with different spring combinations. My P38 7.65 works great with Prvi Partisan but Fiocchi is underpowered and gives me numerous failures to eject (but works fine in my Sig P210 and Swiss Luger). Weird.
I've got schematics for the P4 and P5 too but not the page with the Walther part numbers. I believe that the P38/P4/P38k 9mm use the same springs. I would assume that the P38/P4/P38k in 7.65 would also share the same springs. I don't know whether the P38 and P5 have compatible springs.
Sorry if I've made this too complicated.