http://littlegun.be/arme%20belge/artisans%20identifies%20c/a%20christophe%20louis%20fr.htm

In short it's probably a gunshop/dealer putting their name on the gun. L probably stands for Louis.
As in those pictures you might see another mark on the watertable of the actual maker.

They do say in that link the Louis was a Mechanical engineer educated in Liege and Bruxelles.