First model of socket bayonet with catch designed by Lovell, Inspector of Small Arms. He forced his design in opposition to duke Wellington. The idea was to avoid the locking ring, which he considered too troublesome during drill excercises. A few models of bayonets had this locking mechanism. Finally this passed away, and then came 1853 with locking ring. I have some problem with classification of this bayo, because it fit with dimensions for 1851, but the blade is fullered only from back sides (should be from all tree, according to Skennerton). Made by Heighington. SOcket lenght is 78mm.