This is a socket bayonet manufactured from the period of 1863 to about 1871.
They are very similar to the subsequent Model 1871 for the Swiss Vetterli, but the latter is of noticeably larger dimensions.
These bayonets are also similar to the Russian Model 1891 Mosin-Nagant Socket Bayonet (1st Pattern) and
the Dutch Model 1871 de Beaumont Socket Bayonet.
They have cruciform (4-edged) ~19" blades, blued finish; ~2-5/8" socket length; ~1-1/8" shank. The sight-bridge has a slot machined into it shaped
like an inverted "V".