This is a Marbles No. WEH rear sight for the Model 70 (or any of the lever action Winchester's) It fits into the 3/8 inch dovetail on the barrel. This sight allows for Windage adjustment. It has an adjustable sight height from .520 inches to .620 inches. It has a great feature that allows it to fold down and lay flat on the barrel when not in use -- perfect for guns with mounted scopes.
