Looks like a Pre 1900 European smokeless powder revolver.
Without looking at the old books at the house the closest thing I come up with is something of Swedish make.
I'm Max, from Lille (north of france) (sorry for the short introduction :/ )
Cleaning the basement of my grandfather, I found a revolver that seems older than the Second World War. But there is no indication, no serial number or brand.
Obviously, he still seems to work.
Perhaps you'll find what model it is through these two photos. I know it's not much but I did it now.
I would say it's some type/model of a Lefaucheux pin fire revolver. In any regard I'd say much older than the first world war.
COLLECTION OF 15 EUROPEAN MILITARY LEFAUCHEUX MODEL 1854 ? 1862 MARTIAL REVOLVERS.
Please, if you can, submit clear photos of any markings you find on it: Maker's name, proof marks, insignia, even very small markings.
(No worries: I read French.)
Please also measure the inside diameter of the cylinder's chambers, and the barrel.
I think that it might be Belgian.
It could date from 1860 through 1920.
Keep in mind many Lefaucheux pin fire pistols were made in Belgium with Belgium proof marks, and Spain and Britain. The question being if it has French proof markings, I would assume the pistol is French, as I don't believe the French manufactured Belgium designed pistols.