Rare Alex Martin WWI sniper optical sight

[BurtonP]

Thankfully the Martin rear sight appears to be a standard No 9 sight with a lense inserted. No machining needed. I hope...

[BurtonP]

I found this comment "Aiming points aside, Galilean sights had their fair share of idiosyncrasies. Firstly, focus was adjusted by the convex objective lens. The light passing from the target, through the objective converges on the concave ocular, there it is focused into parallel beams, and enters the eye. However, the concave lens is not actually required, and an image can be formed by using a small aperture, analogous to the way a pinhole camera forms an image."

here: WWI Galilean Sights: An Evolution in Sniping - Guns in the News

With any luck I can use it without the rear lense.
I'm not sure if that helps with other Galilean systems though.