In the case of the Chipmunk, Mk.1 to Mk.9 were reserved for the RCAF variants,
XR219 - that's news to me (which is not for one instant to say that it's not correct), but I'm surprised that it's not mentioned by Hugh Shields who wrote a brilliantly researched and quite comprehensive section on the Canadian-built Chipmunk in the "Chipmunk - The Poor Man's Spitfire" tome.
To clarify, the DHC-1B-2-S5 (the last version of the Chipmunk built) was known in RCAF service as the Chipmunk T.30.