FRF2. This is from the book, FIREARMS CURIOSA by Lewis Winant, which has a photograph that matches exactly, except for the firing pin length, which is shorter in the book.
"Such guns as the Winchester, Marlin, Henry, Volcanic, have accustomed us to a magazine under, not over the barrel. A peculiarity of the repeating pistol illustratrated in figure 298 is the location of the magazine above the barrel. The gun is usually called the gravity feed pistol. It fires a cartridge which is nothing more than a lead bullet hollowed at the base to hold a thin primer and a light charge of powder, quite like a Volcanic cartridge.
The process of getting a cartridge from the magazine to the chamber requires that the hammer be brought to hald cock and left there until the cartridge is fully inserted into the chamber.
Drawing the hammer to half cock raises the chamber block, or carrier, until the chamber is in line with the magazine. Pointingthe muzzle up lets a cartridge slide down to the chamber. A very small rammer, operated with the thumb and forefinger, is provided to insure that the cartridge is pressed fully back. The illustration shows the gun at half cock with the little pivoted rammer having finished pushing the cartridge into the chamber.
When the pistol is brought to full cock the carrier gores down violently and with considerable noise, and aligns the loaded chamber with the barrel. The gun is Belguin, finely finished and ornamented. I can find no maker's name on the example illustrated."
I have no way to scan the photo which is quite small, but with only very small differences in minor details, I feel sure that your pistol is like the one described. Unfortunately, the author does not give caliber. The book is long out of print, and the copyright date is 1955.
I hope this helps some.
Paul B.