The F30B Bofors in the
photo above had Ben Hur style (actually Willys) trailers originally when assembled by Pearsons, and then Pearsons rebuilt the trucks, sorry lorries, into self-propelled units, hence the census number prefix changed from 'H' to 'S'. The trailers were then issued to new GPAs etc.
Note the Allis-Chalmers HST behind the QL. On the right is a Canadian-order GP
W in front of the 20-cwt trailer, hence its 'CMD'-prefixed serial number in the Pearsons'-allocated sequence. The company also assembled US and Britsh GP
Ws!