The 6mm Flobert and 9mm Flobert was very popular over here in Europe at the end of the 19th and the begining of the 20th century for indoor or parlor shooting.
Even now Flobert ammo and weapons are popular in some European countries like the Czechicon Republic, because you don't need a gun permit or licence. They even started making modern rifles and revolvers after the collaps of the iron curtain .

Flobert 6 mm - Weapons and ammunition | AFG.eu- army, military shop