I think the photos found by raffi lack scale. Judging by the scale of the fingers, the relic revolver is not one of the so-called "Montenegrin revolvers"; those were huge guns in the .44 caliber range. Both the unknown and the Liege revolver shown appear to be of the small pocket revolver type with folding triggers. The ivory handled Liege revolver appears to be for the 5.6mm Velo-Dog cartridge and would be a small gun that could be covered by a hand.
Revolvers of that general type were made in Belgium (Liege) by the ton in the late 19th and early 29th centuries. They were also made in Germany, France, Spain, and by crude "factories" in the middle east and places like the Khyber pass area. In the latter areas, trademarks and other marks on European guns were crudely copied and often are unidentifiable as to origin.