Your best bet is to look through the particular war diary of the unit(s) that interest you - but be prepared to be disappointed. I've looked through several (but not all), and some can contain a pretty detailed numbering system, while others have nothing.
It seems too, that regimental tactical markings could have these same numbers as set out for tactical signs of the 8x6 inch variety as found on the Canadian soldiers site.
Above photo example, the same
Q15 can be found on the bumper and within the HQ diamond tactical marking.
Here's an example from
8th Recce in July 1941:
http://heritage.canadiana.ca/view/oo...88/536?r=0&s=1
Further on from the same diary, there is mention of using a three digit system with no letters - see pages 709,710,778, and 779. Also diary
12689 pages 1613,1614, and 1615.
5th CAN ARMD
http://heritage.canadiana.ca/view/oo...52/966?r=0&s=3
Manitoba Dragoons
http://heritage.canadiana.ca/view/oo...16/610?r=0&s=1 pages 610 through to 616
First CAN Army
This one I'm not too sure about, it contains numbers both with and without letters, and are referred to as "Serial Numbers"? Note too some contain two sets of numbers separated '/' which seems to indicate more than one vehicle allocated to the same role?
http://heritage.canadiana.ca/view/oo...77/813?r=0&s=3 pages 813 through to 817
regards,
Jack