Thanks for the comments.
These badges where obviously unpopular, and didn't 'look right' on the fur cap. They where certainly replaced fairly quickly by those Ind/Pak ones, we've seen previously.
Therefore, surplus to fur cap requirements, the Regiment (or QM more like!) being frugal would certainly have reused them if at all possible and as Graham states, where better than on the Pioneer apron. Makes sense to me.
Either way I'm happy it's mine!