I remember when these things were a dime a dozen at Army/Navy stores. We used them for everything: storing ammo, caches, tool boxes, outdoor electronics enclosures, and radio go-kits. The feds started crushing them in the early 1990s, and they dried up. Now you can buy clones at hardware stores, but they’re made in China and not as well-built as the GI ones.
My favorite Army/Navy store just got a batch of the real deal in. If you live nearby and need some, you better move quickly, as I guarantee they are not going to be in stock for long.