This revolver is a bit of a mystery. It is a Gasser-produced, Montengrin pattern model 1874, but it has been converted to use rimfire cartridges - and the specific caliber of rimfire cartridge is unclear. This specific example was proofed in Vienna in 1905, making it a very late-production example. It would have been originally made as a centerfire revolver using the Werndl carbine cartridge, and why it would be downgraded, so to speak, to rimfire is a mystery...