Интерьер кормовой турели FN5A Typical turret mounting of Mk IIIA sight, in this case in a Wellington tail turret. The sight switch was mounted on the starboard turret framing. As can be seen, the field of view was somewhat restricted.
THis drawing illustrates the Type GJ.3 sight mounting on a Nash and Thompson F.N.12 turret of a Lerwick flying boat. A knob on the right side operated a variable resistance to control graticule brightness for night use.