I really believe that the Buck 110 that came out in 1963/64, was the pivotal moment in knife history. Before that, while they had some lock blades around, they were not the everyday norm. Before the debut of the 110, if you stopped 100 men on the street in a pot luck search, I'd guess that 90% of them would have been carrying some sort of to blade jack in the 3 inch to 3 1/2 range. Maybe some serpentine jacks, dogleg jacks, equal end jacks, and so on.
I clearly remember the shift in the shape of cutlery of the 1960's. By the end of the 60's, everyone and their brother was making a clone. U.s. companies, Japanese companies, Pakistan companies, a zillion companies making Buck 110 clones. By 1970, the brass framed lock blade had become the industry standard foldling knife for pocket or belt carry. By 1980, there was almost no slip joint pocketknives being sold compared to the sales of a lock blade. The only folks carrying slip joints like Schrade old timers and Camillus products were a shrinking minority of the cutlery buyers.
It all went downhill from there for the traditional knife market. Companies like GEC and Canal Street came about to cater to a small bunch of consumers, but between the modern one hand folders and the new multitool market, they had the bulk of the buyers. But I do believe ti was the Buck 110 in the 60's that was the stone that started the landslide. In one decade, soldiers, sailors, tradesmen, bikers, hunters, and campers, were converted to the one locking blade knife.
Carl.