The honeycomb grill was, I think, just to keep sunlight out of the box, enabling the aiming symbol to be visible. The display in the sight was just a luminous vertical line and an adjustable-depression (red?) dot superimposed on it. In the HUD, selecting Rev gave you a fixed green vertical centre line. The release cue was a short horizontal line that could be set to the required depression in mils, using a numerical display. Before an attack, you would set the reversionary HUD symbol to the calculated required depression, then adjust the standby sight to look the same. As it is now at least 18 years since I looked at one of these bits of kit, let alone used it, this description is subject to the usual memory fade. If I find the necessary books (now, where did I put them?) I'll get back to you.