The original 52 from the 1920s had a wide dovetail across the receiver and a foldiing leaf sight, like a 1903 Springfield, went into it. As I recall the later 52B was made in two styles, one with the old dovetail, the other with a round receiver. A whole slew of quality receiver sights by Lyman, Marble-Goss, Vaver, etc., were offered in the 1930s, 40s and 50s to fit the dovetail. You will have to keep watch on ebay, under "Winchester 52 sight" and "Winchester 52B sight". They show up fairly often.
