Joseph Robert is contemporary to Casimir Lefaucheux.
Arquebusiers in Paris (1829-1840) at, 17 rue du Faubourg Montmartre and whose workshops are located at 3 bis rue du Coq-Héron.
In April 1831, he filed a patent for the manufacture of a breech-loading rifle.
The little thing sticking out the back of the cartridge is a tube primer. It’s hollow inside and filled with a priming compound that the hammer/firing pin hits to ignite.
You would probably stick one into the cartridge right before you put the cartridge into the gun.