This is a super interesting 12mm pinfire pistol. It is marked with the French Chamelot & Delvigne patent. But is actually made by Eugène Lefaucheux at his Belgian plant as indicated by the Crowned EL and Liège proofs.
It also has an Argentinian gun dealer etched on the top of the barrel — Juan Lopez Buenos-Ayres — and came from a prominent collection of an Argentinian collector, Adolfo Martínez, who pictured it in his book, 𝐸𝑙 𝑟𝑒𝑣𝑜́𝑙𝑣𝑒𝑟 𝐿𝑒𝑓𝑎𝑢𝑐ℎ𝑒𝑢𝑥, 𝑠𝑢 𝑢𝑠𝑜 𝑒𝑛 𝑙𝑎 𝐴𝑟𝑔𝑒𝑛𝑡𝑖𝑛𝑎.
It follows Chamelot & Delvigne’s May 5, 1864 patent and is known as their “Model 8” It is complete with the delicate extractor rod that is often missing on these models. It has remnants of gold gilding various places on the gun and beautiful ivory grips.