AJ Parker Twin Zero M/80 - for which rifle?

[Alan de Enfield]

A pity they couldn't survive with that heritage; "Opticians to the National Rifle Association" at one point IIRC.

The iris eyepiece is not marked by the way, other than an assembly number.

Their products did survive.

My JH Steward eyepiece with 'Iris' (hole size adjustment like a camera) , built in coloured filters and a place to insert a prescription lens.

Lovely piece of kit.

Showing two of the five filters (Yellow & Blue) and Iris almost closed and 75% open.

[Surpmil]

There's something familiar about that setup, perhaps I have another around. Looking through it again the other day it was somewhat amusing to note that unless the mounting tube was cut considerably shorter the iris only began to actually change the FoV at close to the narrowest position. Or in other words, the aperture created by the length and ID of the tube was smaller than that created by the iris until the later was almost at its narrowest setting.

Though on second thought, that would be dependant on eye distance from the iris and the widest setting seems to match the tube ID when the eye is about 4 inches from the iris. Better try that in the prone position again before taking this any further!