This isn’t what we carried on our mandatory twenty mile hike in basic back in 1969. That was heavier and not so fancy.
ALICE packs were issued to field troops in Vietnam in those days and we wished we had them in training but didn’t. The medium ALICE was a rucksack and rode on your back and shoulders, not on your hips like a modern external frame backpack. It was still good, with lightweight water resistant fabric, big outside pockets, and fast opening and closure. I wound up with one that escaped the out-processing in Alaska and hitch-hiked back and forth across the U.S. until I got tired. Also used it for backpacking in the Cascades until I figured out there was something better.
I’ve read the history of this pack but like most military stories it’s kind of involved and boring. The best packs came along too late for the war that caused them to be designed. Now there’s a medium and a large and both are good stuff. The big frame pack was designed for carrying radio batteries and other heavy gear but it’s good for other stuff as well. If you need something to haul out a bighorn sheep’s carcass that big frame could come in handy — just remember to leave the pack itself at camp. That’s the feature that’s attractive about the ALICE pack. It was built to carry stuff, not shave ounces.
Look at an ALICE frame if possible before buying one, and compare it to a civilian version. You’ll notice a slight weight difference and a huge strength difference. I like to test backpacking gear in the store, cautiously, and if I can break it in the store I put it back on the rack. ALICE packs are hard to break. Ultralight hikers scoff at them as being heavy, but sometimes a few ounces in the right place help rather than hurt.
If you buy one online make sure there’s a solid return policy behind it. Army surplus packs vary in quality and sellers do all sorts of tricky things, like selling packs without shoulder straps and charging as much for the straps as the pack. Bargains could be rip-offs. Cheap imported versions fall apart quickly. Expect to pay a reasonable amount for something that’s real — fifty to a hundred dollars isn’t out of bounds.