This is half a nearly 90 year old tin Buck Rogers XZ-44 Liquid Helium Water Pistol by Daisy Mfg. It's corroded on the inside, but sturdy. The outside has a very nice burnished patina. There is some slight warping, perhaps due to years in the elements or the original destruction of the toy.
This could make a great shadow box piece with other vintage science fiction or toy collectibles.