I saw these "can keepers" in one of the Brigade Quartermaster flyers and picked up a few.
I used them to make fire starting kits. The "can" is plastic with an "O" ring seal and a belt clip on the side. I guess it is intended to hold a can of chewing tobacco.
I included 3 alcohol swabs, three commercial fire starting cubes, a small box of strike anywhere matches and a wire saw that happened to fit quite well.
Nice compact backup kit if needed and easy to carry, waterproof(?). Not sure how it would hold up in extreme cold. Not big enough for trioxane fuel bars.
If you feel the wire saw is not necessary in a kit like this, you could replace it with more alcohol swabs.
FSK pics