3rd Century AD portrayal

[jvrjenivs]

I think the book you're talking about is Bishop & Coulston - Roman military equipment, most referred to here as B&C2 (as per second edition).
Another book you might find interesting about later subjects is Alexandra & Gilbert - Legionnaires, auxiliaires et federes sous le Bas-Empire Romain.

Indeed, I would second Nathan's comments. Mail with long sleeves, no lamellar. If you want lamellar and spangenhelm, that is a very good combination, but you should go for a later impression.