In the old west days, small concealable handguns were popular. Something that could be hidden and brought out quickly was attractive to gamblers and women of the night, among others. The fact that they were badly underpowered didn't seem to bother anyone. An example of a popular derringer was the Remington in .41 rimfire. A heavy coat would stop one of those bullets.
But derringers came much smaller and less powerful than the .41, as the model manufactured by Ethan Allen & Co. chambered for .22 Short, illustrates. It is one of the smallest cartridge handguns ever made. It's just four inches long and weighs a mere three ounces.
It's also quite rare. According to the records from the Springfield Armory Museum, only about 300 were produced from 1869 to 1871.
Ethan Allen was at one time a major manufacturer of guns. The company had a factory in Worcester, Massachusetts, and produced quite a few guns over the years — including pepperboxes, revolvers and other derringers and long guns.
Its .22 Short derringer is a single-shot; the barrel swings sideways to load or unload. Pulling the hammer back a little way allows access to the round. There is no extractor or ejector, so having a decent fingernail would be a plus. There is no rifling, but since you are shooting at something a foot or two away, rifling isn't necessary.
The grip is walnut of bird's head design, and there is no checkering. It has no sights, and the frame is made of brass. The firing pin spring is a typical flat type.
The barrel is two inches long, and it's half round and half octagonal.
Obviously, the .22 Short is quite anemic, especially the blackpowder load used by this gun. In a rifle, a 29-grain bullet is propelled at about 750 fps fueled by six grains of a fine-grade blackpowder. In a two-inch barrel, velocity would drop to around 500 fps, producing around 20 ft.-lbs. of energy. That's hardly earth-shattering, but it would be dangerous at close range.
If you were going to shoot this gun, I would stay away from the modern high-velocity Shorts. I'd recommend blackpowder loads or BB and CB caps. It is not meant for a lot of shooting, so keep that in mind if you happen to find one.