Here’s a neat percussion cartridge that Eugene Lefaucheux designed for a gun based on his 1854 patent.
I bought this gun a few years ago specially for the cartridges and have since sold it after keeping a couple of the cartridges for myself. The gun just sold again at auction and is now heading to the Lefaucheux Family Archives.
It was neat because the gun design only took these cartridges and would not accept a regular pinfire cartridge. Even if you switched the cylinder to one that would hold a normal pinfire, the hammer was not flat but partially concave/hollow inside to where it wouldn’t reach a normal pinfire pin (I tried.)