A cyclist pistol

[fernando]

Hi Bill,
Rimfire allright.
Definite calibre dificult to say, due to the wide variety of small ammo developed at the time.
A short .22 fits in rather well. The original caliber could be a "bosquete" or a "flobert" saloon version. The type of amunition without powder charge, the bullit being impelled by the fulminant deflagration.