Prof Plum: the rank braid appears to be wide enough for Fg Off.
Thanks. I've just got home and looked on my tablet and agree with you.
Chris - Glad it helped. A Pilot Officer braid is pretty narrow. On an old Photograph, I think would be less obvious than in your photo.
The dates you have from the Gazette I think you can take as fact. I joined in the mid 2000's and at the time, with a degree you graduated as a Flying Officer, with direct entrants (those without a degree) graduating as a Pilot Officer. That said, things may have been very different in the 1950's - I'm sure there are plenty on this forum who's experience goes back further than mine who can assist. It is also possible to be sponsored at Uni, whereby you get commissioned as a Pilot Officer whilst studying, and subsequent promotion to Flying Officer after that.
I think a subject access request at the first link I posted earlier would really help. If your colleague is a Pre-wings Flying Officer, then knowing the date that he finished flying training (and therefore got his wings), and knowing the date of his Flying Officer promotion will help narrow down the date range.
Not sure what his daughter has - but your colleague will have been given a commissioning scroll, and a certificate when he was awarded his wings. Mine are dated so I assume his would be too. I doubt he'd have thrown those away or anything.
edited to add;
His Flying Logbook would also indicate when he got his wings, as well as last flight in the RAF. Mine had a “record of service” section at the back which details which units I served on, with dates.