The Lefaucheux 20-Round was one of the notable attempts at designing a revolver that offered the operator a pistol with more than a standard cartridge cylinder housing five- or six-rounds of ammunition. This French handgun instead made use of a 20-shot rotating cylinder set up in two rows of ammunition with the inner cartridge chambers spaced closer together than the outer chambers. In addition to this unique two-layer cylinder design, the Lefaucheux 20-Round also featured two barrels, these arranged in an "over-and-under" format. The hammer was large to work the two barrels though only one barrel at a time could be fired with each successive action. In this design arrangement, the operator was supplied a distinct advantage for the revolver featured a hefty ammunition capacity.
Externally, the Lefaucheux sported a noticeably tall profile, necessitated by the large cylinder. The cylinder was set in an "open-frame" design, meaning that there was no bridge present across the top of the cylinder itself - it being left exposed. The hammer was a large single piece and set high about the rear of the body, just ahead and above the pistol grip. The grip itself was a curved affair with grip pattern to promote a better hold. The trigger was a slim lever extending down and curved outward to accept the proper trigger finger angle. A front sight was positioned just aft of the upper barrel muzzle.
The Lefaucheux revolver originated from Lefaucheux's firm out of Paris, France, and utilized the 7.65mm Pinfire caliber cartridge firing from a barrel 4.75 inches in length. The Lefaucheux 20-Round made use of a "pinfire" cartridge developed by Casimir Lefaucheux in 1823 from Paris. The then-innovative design called for the hammer to strike the pin from above, to which the pin would ignite the internal primer and powder, thus discharging the projectile ball. This action, in effect, closed the breech. Pinfire revolvers went on to see extensive use throughout Europe until being replaced by more centerfire-types. The Lefaucheux's cartridge became the first efficient self-contained cartridge.
This attempt at a 20-Round revolver was not a wholly unique design to the French company. Many other late-19th Century pistol firms were forever trying to increase the firepower of the revolver of the day. This particular 20-shot revolver was, however, known to have been used in the American Civil War.