Tallen, you've got all the marks that I can see. Afraid I can't help much.
I have seen a Jean Breuil barrel mark with a Star.....So, going only on this, it may be that M (Star) M is the barrel maker:
I've also seen a "Choke Rectifie" stamp with the barrel borer's initials on it...which may be what you have.
I looked at the 1951 list of gun makers in Saint Etienne but unfortunately there are only last names on it so can't winnow this down further without some additional research. Here are the "M"'s:
Maisonnial Aimé, 13 rue Clément Forissier ;
Manufacture Française d’Armes et de Cycles, Cours Fauriel ;
Manufacture Nationale d’Armes, 2 rue Javelin Pagnon ;
Marnas, 13 rue du Rozier ;
Marsault, 6 boulevard Valbenoîte ;
Martin-Dubost, 38 rue Badouillère ;
Mathieu, 25 rue Badouillère ;
Maumey Jean-Baptiste, 35 rue Mulatière ;
Meunier, 7 rue Jean-Baptiste David ;
Montagny Aîné, 48 rue Gambetta ;
Montcoudiol Lucien (Mécanique), Saint-Bonnet-le-Château ;
We discussed a number of times the "Helice" key. Verney Caron patented a top key and trademarked it three times under various names but none of them were simply "Helice." That word came to be stamped on a lot of French keys, as it came to be associated with "Quality." Larry finally showed what the difference was. A VC top key will not have a slot in the key - VC turned it around so it never needs adjusting. A Scott Spindle top key has a slot in it: