This stirs memories from the 50's. Gerry Mountaineering, at the time a cutting edge innovator in climbing technology, had a blurb in his catalog about producing bags for DOD that were sealed in 'Spam cans," much like the one depicted. I believe he was providing his standard down mummy bag, which was definitely not the GI mummy bag, but a much warmer, lighter, and more compact model -the absolute best at the time.

I know. As a college student, I slept many nights in my mil surp mummy bag, filled with down and light feathers. It was decent, and warm enough, but a tad on the heavy side.

After a stint in the Army as a draftee, I purchased a Gerry bag, and used it for the next twenty years. A marvelous item, it kept me warm down to -30F on several occasions, weighing all of three pounds. It was eventually stolen,or I might still be using it today....
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Geezer in Chief