Re: Anyone able to tell me more about this?
Just FWIW, "tabatiere" is French for "snuff box", so called because the flip open breech resembled the lids of the snuff boxes popular at the time (1860's). The French converted many muskets (I believe that was a Mle. 1857) to that system before abandoning it for the Chassepot. When the muskets were sold off, many thousands were bought by Belgian gun makers who converted them to shotguns, primarily for the African trade, hence the other name, "Zulu shotgun." That is why your gun has Belgian (Liege) proof marks. If they have not been removed, the lock plate should also have the markings of the French arsenal where the gun was originally made.