LeFusil,
I suspect gunmakers young enough for us to know would have served their apprenticeship after the time they had to make files, instead of buy them. My late friend, Helmut Kerner, gave me a hand made "Lauf Hobel"( a special form of file) that his grandfather, Emil Kerner, made . Helmut served his apprenticeship in the factory of his other grandfather( Meffert) in the middle 1930s. His grandfather, then, must have served his in the 1800s.
Mike