This just to say I looked in lots of period references, but came up empty. I tend to agree it’s not custom lettering. For one, something about the spacing suggests to me it’s typographic, And for the other, it feels like I’ve seen this style before. Very likely not Letraset, though. Maybe an alphabet from a sign painting manual that someone turned into a shortlived photo or rub-down alphabet?
I’m adding a couple of names and keywords so that I can find back this thread more easily, in case I’ll come across any leads in the future. It’s a bold signpainter script with letterforms that are rather stuck together than truly flowing, with an r and even a capital F that connect at the bottom. A bit like Salut in this regard, but inclined and more dynamic. Punchline is one of the few script typefaces with such an uptick on capitals – but that’s not it. The top-heavy s, the discreet top of r, and the rather wide k are characteristic details.