When I was a kid, pocket knives were ubiquitous. Every man who had pants on had a knife in a pocket. Didn't really matter if he was an office worker or delivery truck driver. And usually it was some sort of two blade jack in the 3 inch range. Serpentine, dog leg, cigar, or peanut. The smallish two blade jack seemed to be the knife of the era. This was the mid Atlantic area of Washington D.C. and Maryland. There was a smattering of war surplus knives cheap, like TL-29's, MKL knives, and of course scout knives. Some out and out city types who didn't think they needed much knife had those little folded metal handle knives sold near the nail clippers in drug stores, like Trim. One little sheepsfoot blade, or the 'deluxe' models that has a knife blade, a nail file blade, and a combo screw driver and bottle opener. They must have worked, they sold a zillion of them. Pretty common in the late 50's and 60's.
Down on Maryland's Eastern shore it was the same. Smallish two blade jacks. The big difference was that many folks who either hunted, (legal or otherwise) carried one of the little finn type sheath knives. About 3 inches in slim pointy blade, stacked leather washer handles, and made by Case, Western, Kabar usually. The little jack in the pocket was for most stuff, 'saving' the blade on the belt knives for the serious field dressing or whatever. In the country, it was not at all uncommon to see a man with a small sheath knife on his belt. In the city though, when most men wore a suit, the small jack was the over whelming choice. Once in a while you saw a SAK, but they were not common until the early 1970's. Before the backpacking craze hit in the late 1960's, SAK's were an expensive novelty item.
After 1964 it all changed. Buck had the 110 folding hunter, and in a few years, that was all you saw on belts everywhere, even in the city where delivery truck drivers, construction workers, tradesmen of all types, carried the black pouch on the hip. That kept up until Tim Leatherman had his brainchild.
Edit to add, these days I rarely see pocket knives in the hands of people around here. I do see a lot of people using a pen to punch a hole in a package, or a key to saw their way through. Maybe some keychain size SAK's. LIfe in the big suburbia.
Carl.