I used to use these for everything from mixing paint to holding lots of tiny sewing pins. I think occasionally I even had film in em.
I think I still might have a few that were never developed.
It can be used for a variety of things but in fact is the container to hold rolls of 35MM film for a camera.
Uh.... My age is on my profile so I know what these are and I used them quite a bit. In fact I totally muss the days of 35mm