1969 - 1981. Aside from one kid who had a large SAK in 5th grade, I only started noticing knives in junior high (1975-78). I don't recall any one knife model or brand in particular. Saw some Buck 110s and lookalikes. Camillus scout knives. Stockmans. Maybe a Barlow or two.
I never even saw nor heard of Case knives until I was around 34 years old. The brands I noticed being sold in stores (and therefore mostly carried) around here at the time were mainly Schrade, Buck, Camillus, Ka-Bar (pocketknives), Wenger, Victorinox, Craftsman, Colonial, etc. I got my first SAK in '77, a small Wenger with only a pen blade and a nail file. I didn't get my first Victorinox SAK until 1981.
Jim