Ford 3-Ton 4x4 F60B, 40mm AA, Self Propelled

[David_Hayward (RIP)]

I know that I have asked this before but the Pearsons book is now about to be printed ready for Xmas. The photos that I have show F60B Bofors new in Liverpool in 1942-3 with H xxxxxx numbers, towing Ben Hur (Willys) trailers. However we also have later photos from late '44 showing repaired/rebuilds as S xxxxx, for self-propelled (no trailers used). Do you think that the H for tractor prefixes were erroneous or that 'they' thought that they were to be tractors but someone realised that they were not by really any stretch of the imagination? I am pretty certain my Xerox of an IWM Kidbrooke series Bofors has an S prefix number, and no trailer.