This story of Casimir Lefaucheux’s first pistol begins in 1812 when Jean Samuel Pauly patented an early breech-loading pistol and rifle. Casimir Lefaucheux worked as an apprentice for Pauly and began to learn the trade of gun making. There are conflicting opinions on exactly what this first gun was at this time as some modern researchers believe that much of the historical documentation is incorrect, or at least conflates Pauly’s inventions and the inventions of Pauly’s successor, Henri Roux.

What is known for sure is that around this time, Pauly created and patented a system of igniting a charge by the use of rapidly compressed air with a fire piston. It is described in a report by a French military commission on 16 July 1812. This design was also patented in England in 1814 and 1816, where Pauly moved after selling his Parisian shop.

What is contested is if this was also the design of his French patent from 22 September 1812. The patent application does not go into details on how the mechanism works and the accompanying drawings show images of a rifle and pistol that use a percussion piston to hit an early percussion compound. Early reviews of the system and the official recorded record of the patent all speak of this percussion mechanism.

Some researchers think it is unlikely that Pauly created the compressed air version for the military review in 1812 and then pivoted to the percussion version in his civilian model later in 1812 and then back to the compressed air version that he patented in London.