This is this earliest ad I've seen for one. From Boy's Life, November 1964. Notice it's referred to as "New!", so it was likely introduced about this time.
I currently have these in use on two guns, a Crosman 114 and a 400. On the former, the supplied steel shims are needed. The 400 has a larger diameter barrel and I use it without the shims. Crosman also supplied a plastic adapter that was supposed to screw on in place of the rear sight, then the mount was to clamp onto that. Never tried one that way, seems it would be to unstable.
This mount is certainly not rock solid and of course you are limited to a 3/4" scope. Still, I find that they work alright. You have to get them just snug; overtighten and they start to deform.
101, 108, 110, 112, 113, 114 (x3), 118,
120, 140, 160 (x2), 180 (x3), 187, 400 (x2),
Mark II, 1377, 1322, 122CG, Sears 126.19311
312, 342, 397P, 392, Discovery
Blue Streak (x2: '64, '67)
F model CO2 Blue Streak (early production)