From the end of the Civil War through the beginning of World War II, the Stevens Arms Company made single-shot, tip-up barrel pistols in a somewhat bewildering variety of variations and model designations. These pistols were made in both target-shooting and pocket-pistol configurations, some even sporting detachable stocks.
Special care must be taken with those chambered for the .410 shotgun shell, since in pistol or detachable-stock configuration they are considered to be short-barreled shotguns under the National Firearms Act (NFA). This law regulates ownership and transfer of certain firearms such as full-auto guns and short-barreled rifles or shotguns, and requires them to be registered with the Bureau of Alchohol Tobacco, Firearms and Explosives (BATFE), and taxed each time they are transferred. As NFA firearms, the smoothbore Stevens handguns are illegal to possess unless they have been previously registered with the BATFE.
Happily for collectors, most of the rifled-barrel Stevens pistols with detachable stocks, also known as “Pocket Rifles,” have been removed from the NFA list and can be transferred like most other firearms and legally owned without BATFE NFA registration concerns. A listing of these and other collectible guns removed from coverage of the NFA can be found at the BATFE website.
The pistol pictured is not one of the detachable-stock models, so there are no concerns in that regard. It is most likely the Diamond No. 43 Second Issue pistol made from 1896 to 1916. During this time, the company was known as the Stevens Arms & Tool Co. A total of around 70,000 were made.
The frame appears to retain much of its nickel plating and the barrel still has some of its blue. There also appears to be some roughness or pitting on the barrel, which would reduce collector value. I think it would have a value in the $250 to $350 range.