The 2 and 3s were made by a couple of different manufacturers to the same basic spec.
The 4 Mk1 Portables were sometimes known as Triplex (one of the suppliers, or the one that submitted the first basic design).
The 4 Mk2 would have been an assemblage of components. One company to make the trailer (Arrow, Sankey, possibly Brockhouse, GKN, Universal Engineering, etc etc), one to supply the burners/petrol equipment/Latterly the LPG Equipment. The CES will help to identify what was what, and then further dissect via suppliers list/NSN number as far as you can go. But they would have been supplied by a manufacturer/supplier under a specific contract code (The trailers were their own B Vehicle).
Alec