The dust jackets, and bib and braces were worn by a lot of the PHG’s and posties, as we had to work in all sections inward, outward, train stations, and deliveries. And deliveries when I started was two a day, and 2 pouches was a heavy walk! Plus, rebates. The drop frames all had hessian sacks, which was dusty, and when wet heavy a fook, so the dust rackets prevented the uniform getting filthy. But they were mostly worn in the outward.
I think RM now issue grey dust jackets, they’re not the same.
I’ve just seen, via google a RM dust jacket being sold for £75