Those are linked 7.62 NATO blank cartridges, made by Lake City in 1986. They're used by the military for live fire exercises and honor guard firing parties. Still very much a live and potentially dangerous cartridge when chambered, just a cardboard wad instead of a bullet. Definitely not something I'd let children play with. With the visible corrosion on the rounds, probably not too collectable, and I doubt they would all go off when fired, either.