There are a number of gaps in current knowledge relating to wartime Norton WD16H production. They fall between known Ministry of Supply Contracts. One of these is between 10999 and 14000 where only 36 are listed (W11151-W11257)
It now seems as if at least a substantial part of these were sent to Australia and they must have been supplied direct and not via British Army stocks.
Steve S posted a photo on Henk's forum showing ARNs C11230 and C11242 on 16Hs.
The Australian War Memorial are in the process of placing their vehicle records on-line. If only the British had had the foresight to retain their equivalent records, we would have a far better understanding of dates and quantities.
The records show that ARN C11230 was W12359 and ARN C11242 was W12314.
W12315 is listed on the machine pages of this site and is located in Australia. There is clearly lots more work to be done on these ledgers.