The squadron code letters would have been NV. The individual letter may be recorded in the pilots log book which may have gone to relative or appear in the ORB

The serial would have probably come from the squadron operational record book which is held in the National Archives at Kew and are on microfilm.

Failing that Tangmere1940 has been carrying out research for many years and may say he is an amateur in a world of professionals, I think he is as much of an amateur as Hercule Poirot the famous Belgian detective.

Thankyou Thunderbird167 for your help
Saprkyspark