I've added a qualifier to your edit on helmets in Late Roman army:

 Despite the apparent cheapness of manufacture of their basic components, many surviving examples of Late Roman helmets, including the Intercisa type, show evidence of expensive decoration in the form of silver or silver-gilt sheathing.Southern & Dixon (1996) 92-93 Bishop & Coulston (2006) 210-213 A possible explanation is that most of the surviving exemplars belonged to officers and that silver- or gold-plating, or mounted gemstones, denoted rank e.g. the Deurne helmet, believed by some historians to have belonged to a senior officer.Goldsworthy (2003) 202 Best wishes