Originally Posted by
Arkhan Land
Haig and Grimm
for whatever reason in all of the entries I have on mk II and III it says it was harder to repair, maybe more useful as a point in terms of plots than actual real life physics. maybe at the times in RT and 2nd/3rd they just decided the "Archaic" nature of it appealed to the fluff at the time. though granted at this point there were like two or three decent metal models for that jam I dont think they ever anticipated them being for anything more than hobbyists seeking to illustrate the history of 40k. I have a few of these guys sort of just in the general population of my space marines.
as a thought on the heresey model armour thing versus real one, at the time they started to expand that fluff is when they released a bunch of of the torso only versions of a few alternate armour marks, Ide really have to scour my codexes and Stuff Of Legends to figure out which, perhaps at the time GW was trying to explain what would only naturally be a variety of arms being used with these jams, keep in mind this is a super far out weird guess/thought/idea