Feroxeng and Avion Ancien,
Thank you for the images and the additional information.
Fills in a few blanks in my Argus database. The earliest edition of W&R I had must have been the 1963 edition – but it is probably hidden in the attic now.
I must admit to having made the same mistake with a box camera back more than once – and having putting a 35 mm reel through the camera twice whilst on a trip to the U.S.!

FK346, HB592, 598 & 604, all have rather similar final entries on their RAF record card. Typically “S.O.C. Cat.E 29.5.47. F.149/50“.
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Tony Broadhurst