BTW PPK stands for Polizeipistole Kurz (for you German speakers)
To quote Fleming in Dr. No (which you have to respect for no other reason than Ursula Andress' swimsuit)
"Walther PPK. 7.65mm, with a delivery like a brick through a plate glass window. Takes a Braush silencer with very little reduction in muzzle velocity. The American CIA swears by them."
– Maj. Boothroyd, to 007, in Dr. No
I, as an amateur with guns took this to mean the CIA liked them. Per Wikipedia:
"Geoffrey Boothroyd was a highly esteemed British firearms expert and author of several standard reference works on the subject, who is best known to the general public for giving weapons advice to James Bond author Ian Fleming."
"Beginning with A Guide to Gun Collecting and Guns Through the Ages (both 1961) to The British Over and Under Shotgun co-authored with Susan Boothroyd (2004), Boothroyd was a prolific author on the subject of firearms"
That was my limited research on the subject.