Diamond T model numbers

[David_Hayward (RIP)]

My BRANHAM'S book from 1943 shows all the DT models for the civilian market up to 1942-3 and it seems that they had a huge range of models with allocated model numbers. The higher the first digit the heavier the truck. I should imagine that the "9" series was for the heaviest range, perhaps initially military orders, and then the rest were allocated as project numbers to the design office. I would however be inyterested to know if anyone else has an answer.