A29 Canadian infantry training center was Camp Ipperwash.
The S on the upper front of the door just meant Suppressed (for stopping radio interference. )
The numbers are just the post 1943 DND numbers. The numbers for Army vehicles (but not motorcycles) started at 50-001 and went up from there. Yours appears to be 55-961
I also see the remains of MD1, which is military district one...also Ontario. Copied from Michael Dorosh's site:
No. 1 - Headquarters: London, Ontario
1st Brigade Division Counties of Bothwell, Elgin, Essex, Kent, Lambton, Middlesex, Oxford, and the City of London. 2nd Brigade Division Counties of Bruce, Huron, Perth, Waterloo, and Wellington.