Neat. The French were notable for making some "quirkey" guns. I have two of their rather unique double barrel shotguns, both of the sliding breech varity, one a Darne 28 ga is probably the strongest action of the two, it has a hidden, rising bolt that locks into an extension between the two barrels. To open, there are a couple of "ears" on the front upper side of the breech block which you grab and pull up and back. That operates a toggle which opens and slides the breech block back exposing the chambers. To eject spent shells just turn the gun on the side and they fall away. When these were being imported a new one would cost around $13,000. Probably not many in this ga in the US. as they are rather rare.
The other is a 16ga Charlin, not as strong an action as it ismply locks by the toggle locking over. THis is not a high grade gun and was probably a WWII bring back. It has some very moderate scroll engraving around the receiver part and the breech block, When the toggle falls into final closed position the engraving immediately all lines up