This looks like a rimfire revolver. Caliber is hard to tell with muzzle damage, looks smaller than 22 though. There were many rimfire calibers in the late 1800s which would be my guess. It doesn't look like pin fire.
You would have more luck in antiques, with close up pictures of any markings on or in the cylinder. Looks Belgian and inexpensive. The end of the barrel has been sawed off. The ejector rod hole is there, but no retaining mechanism. This could have been ground off and the revolver re-nickelled, the plating looks like it's peeling, which is usually what happened to the re-finish jobs.