Tim,
The serial number is low on that gun, also. All of my Charlins were five digit numbers, 1930s vintage guns, I'm guessing.
Could it be that Louis Charlin got his start producing a Darne copy, which evolved into the (somewhat) familiar "Automatique"? Louis was pretty successful about the time of that catalog, but, perhaps that success had been driven, in an earlier time, by reliance on some even earlier Regis Darne patents.
Much speculation, unfortunately.

Best,
Ted