Re: IVER JOHNSON HAMMERLESS 32s&W
You have an antique first model: If the cylinder is retained by a hook, made in 1894. If retained by threads and no letter prefix on serial under left grip made in 1895. If serial under grip has a B prefix, made in 1896.
Iver Johnson found that the single post lock was too weak even for the low pressure of black powder ammo then used, and changed to the double post lock in 1897. It should not be fired with current smokeless powder ammo.