During WW-II, down sleeping bags were part of the survival gear for pilots in some of the theaters; a late uncle of mine who flew The Hump said that he had one as part of his gear. The sleeping bags were vacuum packed into a small metal can; a bit smaller than a canned ham. I bought one at a surplus store, still in the can, in 1956. I took it out of the container, let it loft for a few days and it seemed to fluff up real nice. They didn't seem to be made for durability, the one I had only lasted a couple of years but the down was still good; it was the fabric that didn't last.