Thanks Philip. Light Fighter Sight makes sense, and this seems very likely. In response to nuuumannn’s request, photos of the interior are given below, along with the 12-pin plug. The clear window looks like it might have had a light fitted below it, but although screw holes are present there is no light. However, there is nothing directly below it which would have been observed, so I’m pretty sure it had a light.

Is anyone able to confirm if this is indeed a Ferranti Light Fighter Sight Control Unit from a Lightning?