Well, the ortho (or at least blue-leaning) sensitization is a pretty big deal; I would focus on that part of the look, foremost. If a suitable film isn't available, then you can put a cyan filter on a modern film and get pretty close. Once you see what you get in terms of skin tones, then you will see why I strongly suspect paper neg retouching.

When did red sensitization appear? 50s and 60s? All I know is that it was amazingly recent.

P.S. Nope I am off by ten years it seems.... look at this!