Nouvelle page 0
This site has alot of info on Belgian mfg'rs. If there is a name on the shotgun, try finding it on the 'Identified Craftsman' link.
Sometimes makers marks are only small initials stamped on some guns w/retailers markings being boldly imprinted.
The action type is sometimes called an 'underlever snap action'.
There were variations using a side lever and others.
Generally the lever motion unlocked the action only on a hammer gun but occasionally some patents made for the hammers to be retracted to half cock also.
On a hammerless design, the lever motion moved the internal hammers to full cock of course.
Most all of the English 'name' shotguns can be found with variations of the design at some point.
Careful study of the proof marks can give you a time frame of mfr. You probably have that already. Sometimes the mfg'rs mark is not prominetly made depending on the grade of the gun or it's intended market.
Like some German and Austrian makers, it may only be a simple set of initials sometimes in an oval on the action flats or bbl flat and a name on the rib or barrels may be a retailer of the gun.