Eye Tests
Thanks again for the feedback.
PZU: At the time, the minimum "Night Visual Capacity" for a pilot was 13, whilst an Air Gunner was 8, which may help explain your father's experience.
Danny: The test results are handwritten on the front of some service records so you may be correct as Turret and Tunnel look very similar when written.
It was the "turret" notation that prompted me to try to find a list of the eye tests carried out.
Regards
Pete