Here are the two PPK variants -
This is the original PPK - this particular one made during WWII, a war bringback by a P-47 fighter pilot friend who willed it to me. The "K" stands for "kriminal" - for
criminal detectives to carry more discreetly.
And this is the PPK/S - or "Sport" to meet U.S. importation criteria - a PPK upper and a PP (Polizei Pistole) lower.
John