Here is an excellent artifact of the Civil War: a Model 1855 socket bayonet. This was a state of the art weapon issued for Federal issued Civil War .58 calibre rifle muskets. These were made at both national armories and were required for every rifle musket acquired from contractors.
Its nearly 21" overall length and finely designed locking device made the weapon a formidable extension of the standard shoulder firearm of the Union forces.
For more detailed information, noted authority Paul D. Johnson wrote a comprehensive five-part series for North South Trader's Civil War magazine covering all types of bayonets used in the war by both sides from socket bayonets to sabre types, domestically made and imported.
This non-excavated example has a small letter "S" stamped beneath the bold "US" in the ricasso.