This is basically the French Model 1840 but with a "cock's comb" upper finial on the muzzle-ring end of the cross-guard, a re-designed external spring-steel latch, and slightly longer blade - ~22-3/4" as compared to the original length on the 1840 of ~20-1/4". These bayonets were widely copied and used by many countries - including the United States, Belgium, and Germany. Many of the actual French-marked bayonets can be found with German manufactured blades. It is believed some of these were used during the American Civil War when many European arsenals were emptied of their surplus arms.
These bayonets were manufactured from 1842 to about 1866 at which time they were superceded by the French Model 1866 "Chassepot" Bayonet.
This bayonet is brass-hilted with a spring steel latching arrangement on the right side. The crossguard is iron (steel) and with a "cock's comb" muzzle-ring finial. The lower quillon is a hooked "blade-breaker" type.
The blade is steel, single-edged, fullered (both sides), with a re-curved or "yataghan-shape." The blades are usually marked on the back-edge (opposite the cutting edge) with the arsenal, month, and year of manufacture; this is done in engraved cursive fashion and will appear something like, "Mre d' Armes de Chatellerault Janvier 1842" or perhaps "Mre d' Armes de St. Etienne 8bre [October] 1847".
There are several variations of this bayonet and they were produced in substantial numbers. The scabbards are usually blued sheet-rolled steel with a ball finial.

These bayonets were eventually replaced by the French Model 1866 "Chassepot" Sword Bayonet (and corresponding infantry rifle).