The "Tom Thumb" is a tiny .22 rimfire revolver made in Belgium by an unknown shop and imported into the US to be sold by the Daly Arms Company of New York. These are antique guns, probably made in the 1870s or 1880s, chambered for the original black powder .22 rimfire cartridge. There are other similarly sized guns (like the Colt New Line rimfire revolvers), the the use of a ring trigger here is quite unusual. The ring appears to be too small to actually use, and in seeming acknowledge of this, the front face of the ring is textured for grip. Why these revolver didn't use the much more practical sheath trigger is a mystery...