Different Canadian toolboxassemblies...why?

[Darrin Wright]

The other day I took up the offer of the plans etc to build the toolbox assembly on offer by George on MLU. To my dismay, I have now discovered that there are two different types of toolbox assemblys and when looking through my reference pictures that I have collected off various websites, there appears to be no pattern as to what truck had which toolbox.
Which toolbox was the early one? or, were they made by two different companies? or, left over items assembled onto trucks in any order?
In time I would like to mount a Canadian toolbox/tyre carrier onto my Dad's Canadian bodied C15A with Aust sunshine roof.
I have attached two photos from oldcmp.com that depict the different style of toolbox.