Hi Geoff,
I am looking at Rootes parts list no 437A, it covers British Army contract 6/VEHS/7878/CB27A for Chassis no's 38A0001 - 38A3499 and 38A5000 - 38A5200, with body types, Cargo, Command Workshop, Predictor, Recovery, Tipper, H.P. Recuperator, Radar Repair, Telecom Repair, Fuel Injection, Electrical Repair, Instrument Repair, Armourer, Cypher, Signals Office, S.D.O., Crystal Main. Note your 38A number does not fall in to these chassis numbers. The first number you quoted was 31A, if this was a mistake, and should have been 38A, then it is part of this contract. It would be interesting to know where these two plates were fixed to your vehicle. Any photos?
There is another of these, unless it is the same one, in the South Australian MV Museum, at least it was when I visited it in Port Adelaide in '95. Museum has relocated now.
regards, Richard