I picked up this one a couple years ago.
This is a 16 gauge Lefaucheux pinfire shotgun. Like many early French guns, the barrel was made in Belgium. This particular barrel was made by Fassin & Ronge sometime after June of 1853 as that is when the EL export proof was first used. Casimir Lefaucheux’s died on August 9, 1852 so the gun was made by either his widow or the shop’s successor, Casimir’s son-in-law, Laffiteau. It was made before 1865 when Laffiteau registered his own marks.
And a video!