George,
It is possible that it was converted from LHD to RHD by the army. Whilst working in REME workshops, I built up the Royal Salute vehicles ( 5 x Series 3 Lightweights) for the Honorable Artillery Company. These vehicles were in a very used state before work started and I did note that one had LHD on the nomenclature plate, although it was actually RHD......so you see it could have been done whilst in service.
Another thing that comes to mind, and I have not much spent time on Land Rovers in more recent years, is that on original chassis's, there is only one position for the steering relay, thus dictating whether the chassis is Left or Right hand drive, whereas a replacement chassis is universal with two mounting positions. I may be talking a load of rubbish here, but am sure CW or Nick will put me right.