[Trooper117]

On another related tack, I've just been checking in Bud Andersons book 'To Fly And Fight', that his group began to replace the B/C model for the Mustang D model in May1944.. The fitting of the K-14 gyro sight started in June 1944, all done localy on site.. So clearly, the initial D models didn't arrive with them factory fitted... Also, D models appear to have been introduced as the earlier B and C models became u/s or were written off, so logic dictates there may have been earlier models that were fitted with the K-14.. Anderson states that he prefered his old model and kept it, even though he could have had the newer D model. He kept flying it until he went home on leave, then recieved the newer D type on his return!.
The info above applies to the USAAF of course and not the RAF, but it does give an idea that no matter what official accounts may say, the men at the sharp end often modify their own equipment to suit their needs, regardless of what official higher formation instructs them to do..