Orange cardbacks were Ral Parthas first battletech / battledroids offerings, many of these sculpts were closer to 1/144 to go with the plastic kits..then later were resculpted down to Z/GHQ 1/300 scale. Anyway someone has listed a bunch on ebay...at 100 bucks each. Bastards. All the track and wheel and hover vehicles were radically redesigned when the vehicle technical manual was released, and are on blue card backs.  About a third of my original figures were orange cards.