Looks like a pretty basic French guild gun (no maker's name--not at all unusual with French guns). Very odd cheekpiece! That's more of a German thing, usually. The "portee garantie" means that the range is guaranteed, although who knows what the "guarantee" is! The mark on each barrel in front of the flats, where it says "St. Etienne", is single (ordinary) French proof.
You've got yourself a shooter, with appropriate light loads. You might want to check the chokes. They're often very tight on French guns.
