Regarding ARN font question raised by Jacques: The ARN font, and the position of the ARN on the front shell panel, varied between production plants according to local practice. The plant can usually be determined from the ARN record, which gives the State or Military District where the vehicle was first issued. Unfortunately it's often given as 'VB' for Victoria Barracks, which is rather confusing because there are Victoria Barracks in Melbourne, Sydney and Brisbane. It's a particular problem in the 52xxx - 555xx range, which is what we're dealing with in this case. Perhaps Mike can shed some light on this question.
Comparing VB ARN 53166 to NSW ARN 55936: the 3, 5, 6 digits look virtually identical to me, possibly reflecting an individual Ticketwriter's 'signature' as described by Tony. The WA ARN 59877 looks like a different 'signature' to me, ie. fatter and flatter, with a pointed upswept tail on the 9 digit. Two of these ARNs are centrally placed, leaving insufficient room for the Formation sign and TAC sign if required.
Other States including VIC and QLD used stencils, and placed the ARN along the top of the panel, leaving plenty of room for the Formation sign. However these stencilled digits were quite large and well spaced, which meant 6-digit ARN barely fitted across Cab 13 panel, unless it contained another '1' digit. This seems to have led to diagonal placement occasionally - Keith's gun tractor ARN 134855 may be an example of this practice. Postwar stencils were somewhat narrower, perhaps deliberately so for this reason.
Interestingly, just like Ford practice, Chev ARNs were stencilled in VIC but handwritten in NSW. In both plants however the placement was along the inner side of the panel.
These are just my own observations over time, not based on any proper study of the matter. In the interests of authenticity it would be worth conducting an investigation of ARN fonts and placement on CMPs, perhaps using this thread commenced by Jacques to post examples and discuss.
Cheers,
Tony