The back brace arm is part of the plate. When it was manufactured, the stamping cut a tongue in the back. If mounted flat against rear panel of vehicle, one left it untouched. If mounted on front, e.g. Cab 11 or 12 CMP, one folded it back so that bolt hole fitted under headlight leading edge so headlight mounting bolt could be removed, the plate brace slid in, then the bolt reinstalled. The two variations shown in photos above simply show how soldiers bent the back brace.
Have a look at my web site's page on Cdn vehicle markings.
http://bcoy1cpb.pacdat.net/markings_...y_vehicles.htm
The CAUTION LEFT HAND DRIVE is a separate issue.
COLIN