I have one of Tom's improved H&H cocking piece sights for my .404 Jeffery project. Here's a vintage H&H in .30 Super Mauser wearing an original...
H&H cocking piece sight

Also here are two picts of the Mauser tang sight that was referred to earlier:

the Mauser (also used on Mannlicher Schoenauer) popup in-the-wrist sight was called a Bailee-Grohman (if I have spelt it correctly).