This is a take down screw and saddle ring for the Winchester Model 9422. This particular version has a BRASS saddle ring and Blued screw/stud.
It fits the .22, .22 magnum and .17 HMR. It replaces the factory take down screw which requires a screwdriver or coin to remove. This piece adds the functionality of a saddle ring and allows you to take apart your rifle with no additional tools.