Nomenclature suggestion:
“Full stocked” swivel breech and German “wender” rifles usually have one-piece fore stocks made with two barrel channels inlet into them with a thin and delicate (frequently 1/8 “ to 3/16”) portion of the stock separating the two channels. I strongly prefer the term “full stocked” for these fine pieces, like this spectacular Wm Shreckengost rifle. If Shreckmeister Rob showed a close-up of the muzzle, that would be apparent.
Many later (percussion, usually) swivel breeches have the barrels fastened together with solder or bow-tie wedges (and frequently with iron, brass, or less commonly German silver ribs). Quite rare ones of those have separate wood “panels” applied between the barrels like ribs. Those can be properly called “full paneled” in my opinion.
Bill Paton