So following the logic of the numbering of the variations being offered.
Packs one in either grey or brown livery in the range 26001-26123 with corrugated ends and flush sided doors, represent the first iteration.
Packs three, in either grey or brown livery in the range 26185 - 26208 with corrugated end and panelled doors, represent the second iteration.
Packs two in either grey or brown livery in the range 26381 - 26487 with cross braced ends and flush sided doors represent the third iteration. These packs also include a fourth iteration as some of the later wagons had VAC pipes, in model form these are 26405 & 26430 in grey and 26422 in brown. However the latest running number 26487 in brown is not described as having vac pipes, is this correct?