While you are on the site, in your browser find and click "Add to Home Screen" A CGN beaver app icon will then be created to your phone that is directly link to the site.
Note: This feature may not be available in some browsers.
If it's an original Lefaucheux, it might be one using pinfire ammo which is waaay long gone.
Lefaucheux had also a patent on pinfire shotguns if I recall well.
PP.
It is definitely not a pinfire; they have notches in the cylinder for the pins and the hammer strikes down not forward. I would strongly suggest using some parafin wax and taking a chamber cast plus slugging the bore so that you know what dimensions you are dealing with. Also measure the gap between the cylinder and the frame to establish the rim thickness of the shell. Follow up by going through cartridges of the world to find what you can make the shell from