The Lefaucheux model 1859 carbine was a small carbine Eugène Lefaucheux made with hopes to gain military acceptance. It is a very simple design with few moving parts. It only weighs 4.5 pounds and has an overall length of 3 feet 4 inches.
There are multiple variations of this gun; some with a full metal frame, some with an automatic cartridge extractor, a percussion cap version, a double barrel version, pistols, and various bores.
This example is chambered for 12mm pinfire cartridges, has a manual extractor and a solid wood stock.
There are two levers on the gun. The one on the right is the cocking lever and also serves as the breechblock. When you raise it it opens the breech, allowing you to insert a new pinfire cartridge or remove a spent cartridge. It also cocks the extra-long hammer. The following video and image shows how this works.