Very interesting, I didn't know either.
You mentioned that those pin-ups of the fifties were giveaways with company logos.
My next project will be Revell's 1952 Büssing 8000 kit. It has a nice decal sheet including a pin-up girl for the grille as the instruction sheet says. This Revell pin-up has no company logo.
Were there also pin-ups without company logos or is this Revell decal something like a generic pin-up without real reference? If it is historically incorrect I will rather leave it out.
No more stupid questions from me in this topic - scout's honour!