Early Canadian Mechanisation
 

In the late 20s, early 30s, the Canadian Army trialled trucks from GM, Leyand and Thorneycroft as tractors for the 60-pdr Medium Gun.

http://www.servicepub.com/images/dsc03179.jpg
This truck is already in Artillery service. It is marked B / 3MED RCA / T-2

http://www.servicepub.com/images/dsc03183.jpg

http://www.servicepub.com/images/dsc03181.jpg

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Above and below, Thorneycroft

http://www.servicepub.com/images/dsc03189.jpg

http://www.servicepub.com/images/dsc03182.jpg

http://www.servicepub.com/images/dsc03196.jpg
Leyland Terrier
http://www.servicepub.com/images/dsc03192.jpg
General Motors

GMC
 

I suggest that the General Motors Truck was a Thornton conversion [Thornton Tandem Axle Corporation, Detroit]. Leyland had a subsidiary or agency in Leyland Motors Ltd [of Toronto I think], but the Thornycroft is a new one on me!

These trials are very similar to the 1930s ones by the War Departrment: see VINTAGE ROADSCENE magazine. I have written on the 1936-7 Trials and the next issue in the series has photos of 1935-7 Trials, recently found.