Linothorax vs Quilted linen vs spolas

[Paullus Scipio]

John Conyard wrote:

Therefore I think it could be safe to assume the artist was trying to illustrate two differing armours, rather than just painting on the pteruges at a later date. The monument is early 4th century.

....I don't think it would be safe to assume this at all, because even a casual inspection of the real thing ( beautifully displayed in the British Museum) shows that, like all other major ancient monuments, a number of different sculptors were at work. It would be far safer to assume that the same type of body armour is being depicted in different ways by different artists.
BTW, it should be noted that later Tube-and-Yoke corselets, both Greek and Macedonian, show a style difference from earlier ones in that the waist tends to get higher, and the pteryges longer......