Lancaster, apparently you haven’t read the article in "Der Waffenschmied" on the history of the so-called "Collath" slide-and-drop action. That percussion breechloading gun on littlegun.be is not by Collath or Teschner. Look at the inscription on the top rib. The word “MEHLIS” is legible, so it was made there. Neither Wilhelm Collath nor his father in law Gustav Teschner ever worked in now Zella-Mehlis. This capping breechloader is made to Renette’s French 1820 patents. Renette’s capping breechloader is the “grandfather” of the “Collath action”. Such guns were called "Schnellader" = quickloader in Germany and used muzzleloader-style cartridges, powder, wad and shot wrapped in paper, as Daryl S already noted.. Ignition was by hammers hitting percussion caps on outside nipples. As such cartridges had no case or base wad, gas sealing was achieved by steel cups or tubes entering the breech ends of the barrels. Of course such gas seals needed a straight fore and aft movement of the barrel before they dropped on opening. Such capping breechloaders were made by Gastinne's father in law and partner Albert Henry Marie Renette, who obtained two French patents for outside primed guns with slide and drop action in 1820, way before Lefaucheux' invention of the break-open gun, 1834. Not only Gastinne-Renette, Paris, made such guns, but the design was copied by many other gunmakers all over Europe, as in the “Mehlis” signed gun erroneously ascribed to Collath by littlegun.be.

Contrary to popular belief neither Collath nor Teschner invented that slide-and-drop breech action. The merely took an existing breech action and adapted it to their own needs.
These slide and drop actions are now so linked to the "Collath" name that even guns by others, some predating Teschner and Collath, are labeled "Collath" nowadays. But neither Gustav Teschner nor Wilhelm Collath invented this breech action. Teschner first offered needlefire guns in 1858. Five years earlier, in 1853, Louis Julien Gastinne obtained the French patent No.9058, showing this breech action on a hammer gun, intended to use inside-primed centerfire cartridges. Subsequently the patent agent Auguste Edouard Loradoux Bellford patented the same thing for Gastinne in Great Britain, patent No.2778 of 1853. Bellford assigned this British patent to Charles Lancaster, London. Lancaster popularized these hammer slide and drop action using Gastinne’s inside primed “base-fire” cartridge. Even Gastinne did not invent this breech action. About 1850 the young gunsmith journeyman Rudolf Berger from Köthen worked at the Gastinne-Renette shop in Paris during his travelling years. After returning home he took over his father's shop and made needlefire guns of his own design. He simplified and improved Nicolaus v. Dreyse's coil spring striker locks and combined them with Renette's slide and drop breech action. As his own paper needlefire cartridges still lacked a gas seal he retained studs on the breechface, but with Chassepot-type rubber cushions for better seals. By placing his primers near the rear end of the cartridge instead of Dreyse's position in front of the powder charge, he could use shorter, less vulnerable needles for ignition.
Only now enter Gustav Teschner and Wilhelm Collath. Legend has it that Collath, working for Teschner since 1855, actually developed the "Teschner-Collath" gun. Coil spring striker locks were deeply mistrusted then by many gunmakers, accused of slow lock time and weakening coil springs. So Collath took the basic Renette slide and drop breech action and combined it with tumbler locks powered by large leaf springs, mounted on the triggerplate. These are the earliest hammerless Blitzschlosse = triggerplate locks known. The locks are cocked by the underlever when opening the gun. Turning the wing-nut shaped safety on the tang blocks the inside hammers. As the Teschner-Collath nailfire cartridges now had a metal base cap and a solid, gas sealing base wad, Collath did away with the Renette-Berger breech sealing plugs on the breechface. The base wad and a metal cap was alredy patented in 1846 by French Houllier of Paris.