+ Just about any Anschutz sight WILL fit any HW made after the late 1970's, which have the same 11mm groove spacing. Older HW's have much wider (13mm) groove spacing, and basically nothing fits except their own old sights.
+ FWB sights will NOT fit. They are about 11.5mm, plus they have a crossbolt that mates with transverse grooves in the top of the recevier.
+ Older "round" Walther sights will NOT fit. Also 11.5mm, also have the cross grooves.
+ Newer "square" Walther sight WILL fit. They have a single mounting "foot" on one side and are farily tolerant of minor groove spacing deviations.
+ Old Diana sights will NOT fit. About the right groove spacing, but made for a shallow flat rail. Not enough vertical clearance for HW's round-top receiver tube.