In the early 1970s the outdoor equipment industry was changing rapidly. Kelty backpacks were the premier backpack, with others made by Jansport and Alpenlite being quality brands. REI made a Cruiser which was a cheap imitation of the Kelty. The packs of that era were not called external frame backpacks, because there was no internal frame backpack to require the distinction.
John Robinson and Jim Lawrence were working for Kelty designing new products, and the project headed by John Robinson was the Tour Pack, the world's first internal frame backpack, first sold in 1973.
The Tour was blue, and appeared small and simple compared to today's internal frame packs, but you can definitely see it is the genesis of all those that followed. Alp Sport, Gerry and North Face had pack swith some sort of bendable aluminum stay, but they were primarily ruck-sacks with no viable hip-waist suspension system. Shortly after the Tour Pack came out Choiunard made an Ultima Thule, and Gregory and or Rivendell soon followed with similar packs.
Kelty sent models of the Tour Pack to myself and Ned Gillett, who both gave it high marks. John Robinson and his climbing buddy Steve McCarthy did a nine day winter transit from Mammoth Mountain to Yosemite Valley on skis using the Tour Pack. That was with winter bags, tent and lots of food, on x-country skis over interesting terrain. The packs worked perfectly. The side pockets of the Tour served as ski holders, and you could slip your skis behind the pockets. The bottom compartment was a zippered sleeping bag compartment. The pack had leather patches for securing skis, crampons, and ice axe. The top flap and rear panel had zippered pockets.