Belgian-made by the hundred-thousand between late 1850's and beginning of the 20th century, and designed to shoot .22cal CB caps IF the barrel is actually bored hrough. Or, if you can find them, Flobert .22 blanks.
I had one as a child. They were mostly found nickel-plated and ranged in quality from not-so-bad to appalling. They were known as 'birdhead pocket pistols' because of the shape of the grip.
If it IS bored through, in THIS country alone in the world, it is classed a a firearm - CB caps are still available on sale in this country.
Other real collectors wil no doubt join in.
tac