I am certainly no expert, compared to the collective knowledge of this group, but in my time working at an artillery site I have never seen a gunner wear his guns in this manner.
However, like you say, you can never be sure what was done in the field. It just stikes me odd that a senior NCO would ever do this for any length of time...if it was a simply shortage of badges, I could see the good Sgt. boxing the ears of the poor lad working in the QM stores!
I will keep my eyes out in historic photos for you.
Cheers,
Bob
PS A very nice collection that I would be proud to own.
Fort Rodd Hill & Fisgard Lighthouse, National Historic Sites of Canada
Parks Canada