Well, my curiosity got the better of me and I Googled 'zerust bags'. And, lo and behold, it came up a real item.
It is a rust-prevention storage container, a bag, for ferrous metals, specifically pistols and rifles. It sounds as if it would do a good job protecting your firearms from any deterioration, but it takes away the fun and joy you get from taking your revolver out, fondling it, cleaning it, relubing it, and putting it away again. Plus, your weapon is not readily available if needed. I think I'll pass.