I've been thinking about this for a while.

Basically, marines most often have their chapter symbol on their left shoulderpad and a squad type marker (and squad number) on their right shoulderpad.

A Mk 6 marine (who has a studded left shoulderpad) carries their chapter symbol on their right. (I know, sometimes with a squad marker behind).

A terminator carries their chapter symbol on their right shoulderpad and the crux terminatus (effectively a squad marker) on their left.

But a veteran in power armour (who remember, presumably also wears terminator armour sometimes, or, at the very least, is entitled to) wears his chapter symbol on the left and a squad type marker (the crux terminatus) on his right.

I know in terms of real world history. The Mk 6 marines were sculpted first, then the terminators, then the Mk 7 marines (iirc, were there one-off exceptions?). So in terms of real world history: Why did they sculpt (okay, technically paint/draw) the Mk 7 marines with their shoulderpads back to front compared to the earlier terminators?

And in terms of fluff, why do the terminators wear their shoulderpads back to front compared to Mk 7 marines?