It's a constabulary revolver.
Probably Belgian made, based on the safety.
Every European constabulary force with aspirations used copies of these through the turn of the century unless they had enough money to afford Nagant revolvers or knockoffs, or unless they had a mandate to use something specific and/or domestically designed.
I even have a mystery piece in my store in 7.5mm Belgian Ordnance, or 7.5 Swiss (7.5x22 vs 7.5x23, and similar enough to be interchangeable-sometimes?).
The smallest caliber I have seen was 6.35 MM, and the biggest was in 11mm French Ordnance, but they were chambered in pretty much every center-fire or rim-fire cartridge in between (I've seen 41 RF, 8mm Lebel Pistol, 450, 452, 455, 10.4, pretty much every bulldog caliber, .380, .320, 9.4 Dutch, .44 Russian, 38 Colt, 38 S&W/.380 British, and many more)
If you know the approximate caliber, we can probably narrow down where it was used.
