Probably a pinfire design adapted to center fire or rim fire cartridges.
Sort of like the Remington conversions of C&B revolvers to fixed ammunition.
That way they could use up parts and tooling leftover when the pinfire cartridge fell out of favor.
This pistol reminds me of a pinfire bought in quantity by the US during the Civil War. Despite sturdy construct in pinfire form the cartridge was so weak that as one trooper put it "you couldn't even kill a pig with it". He'd actually tried to kill a pig caught by foragers and emptying the pistol into it had no effect.
One artilleryman shot a Confederate officer in the head at point blank range and only knocked him out. The officer was wearing a hat to large for him so he had placed folded newspaper in the liner to get a better fit. The bullet cut through the hatband and was stopped by the folded paper. Aside from a concussion and large bruise the officer suffered no real injury.
The pinfire system took up a lot of space in the cartridge case so little room was left for the powder charge.
The basic design of several types of pinfire pistols were carried over into the centerfire designs, sometimes using very powerful centerfire cartridges like the massive Monte Negrin pistols that used a cartridge intended for carbines.