This is an ORIGINAL friction stud Winchester 1894 pre 64, model 64 and model 55 lever action rifle. This little part goes into the back of the link. The friction stud spring (wp708-a) sits under it, and both are held in place by the friction stud stop pin (p142). This assembly snaps into the receiver and keeps your lever in the closed position. If your lever falls down or sags the stud might be worn.
