The missing front sight likely looked much like the one on the revolver in the second link posted by S&WChad. Kind of an Eiffel Tower look.

Belgian made is a best guess. Usually covered in proof marks. But it's not unkn for those to be missing from some specimens the left the shops through the back door.
The one and only Crown/K mark reminds me of some Scandinavian proof/inspector markings.
Even Dutch inspector marks, but the Dutch inspector marks which are just that, a 'Crown/capital letter' are generally a much smaller and simpler crown figure from what I recall of Maastricht and Hembrug arms inspector markings.
Some of the Dutch gunmakers had some of their frames and major parts made in Leige, Belgium and then finished the construction of the guns in Holland. They can carry the Belgian makers mark under the grips at times. Usually just a couple of initials. Nothing fancy unless they are the primo makers like Francotte.
The Steyr Works in Austria used a 'K' as an inspection mark on rifle and handgun parts,,,but it does not have a Crown over it.