I'm not going to be able to get a William's peep sight anytime soon, so I swapped it across from the Norinco. The odd width of the Henry Dovetail makes the sight biased to the left side as the sight element is centred over a 3/8" dovetail - the Henry seems to be significantly wider, though I haven't bothered measuring it yet.
The diopter effect instantly improved the sharpness of the front sight, though it is still a little "furry". I went out and zeroed it with Eley Standard at 50m. The aiming marks are smaller than I prefer at 50m, but the first group was about 50mm left and 100mm high.
As the rear sight graduations are dependent on the sight radius of the rifle I have no idea what the clicks might equate to, but I increased the aiming point to three thicknesses of insulation tape, and dialed the knobs to get it pretty close, while allowing about 15mm of wind from the right. The elevation bottomed out early, 50mm high at 50m, very annoying as it throws out my holds.
So I fired a last group at 40m offhand to confirm and it's 50mm high there as well.
I guess it'll be close to a 75m zero.
The Henry front sight is cast plastic so I'll have to think about how I can increase the height. I also need to narrow it, but it can be difficult to keep a sharp edge when filing plastic. The simplest might be to drill and tap a screw into the plastic ramp.