The gun is a pinfire; while ignored and denigrated in the U.S., the pinfire in Europe fell into the same chronological era as the rimfire in the U.S. and was as popular and common. Those revolvers ranged from near junk to well-made guns, to works of art. They were made by the ton in Belgium, France, Spain and Germany. That one appears to be a "dug" gun and in that condition it would be difficult or impossible to determine the origin.
The "cartridge" (or cartridge case) is a new one on me. It does not appear to be a small arms cartridge at all; it might be an auxiliary cartridge for something like a mortar or a rocket launcher.