Found this thread with letters prefixing regimental numbers ... apparently "C" represents MD3 (Military District Three if I interpretted this correctly? Not sure if I did so verify with others who know for sure. Military district 3, I assume, is Ontario if your "relative" was from there at the time of enlisting, but that must be verified by someone who knows the numbers etc. I don't have a copy of Clive's book to do a lookup for you, otherwise I would, just to verify or not

Regimental Numbers

The same thread mentions Clive Law Service Publications who has published a book about service numbers!!!

Law, Clive M. Regimental Numbers of the Canadian Army, 1936-1960 (Compiled & Edited by Clive Law, Service Publications, Ottawa, ISBN 1894581024).
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