This will get you started
https://www.shotgunworld.com/bbs/viewtopic.php?f=5&t=232252

Possibly Charles Masquelier
http://www.littlegun.be/arme%20belge/artisans%20identifies%20ma/a%20masquelier%20gb.htm

By the font I suspect C&M was the importer. Is there nothing on the rib?

It was made 1910 to 1921; there is no lettre annale