I got to the Argosy in the middle of 1962 and I have a recollection that the loadmasters were all volunteers and came from various trades. They didn't have a proper brevet but were given flying pay.
I can distinctly remember that two of them on 267 Squadron were still wearing their wartime AG brevets and I think one of them had a DFM.
I have an idea that the QM brevet came along in 1963?