[Tony Smith]

The "C" plate became the ARN system.

Pre-War, Australian Army vehicles were issued with Defence Department plates, that had the format of: DD, then a red Broadarrow, then a 2, 3 or 4 digit number.

Sometime around the outbreak of the war (Pre- or Post- ?), a new system of Commonwealth Plates arose, being a red C then a 3, 4 or 5 digit number. For the Army, these were only issued to vehicles of the Militia Forces or the Permanent Staff, for vehicles that were intended to remain in Australia.

When the AIF was formed, it was naturally intended that the Troops and their vehicles were to serve outside of Australia and a system mirroring the WD system of vehicle classes was used, in the form of AIF in white then the vehicle class letter in Red, the the number in white, all on a black background.

After the Japanese entry to the war, the AIF registrations were gradually transferred to the C System over a period from Dec 41 to Mar 42. Through convenience, omission or directive, over time, the C was dropped from the number and it became the ARN, although other Commonwealth Government Departments continued to display the C. There are several examples of the same vehicle being registered under the "DD", "AIF", "C" or ARN systems at different times.

The C number on this bike is either an AMF vehicle from 39 to 41, or any Army vehicle from late 41 to the end of the war. Looking up the number in the AWM records will indicate the actual date.