Shining/Polished/New vs Worn/Weathered/Used Armour

[M. Demetrius]

All those bits of brass on a lorica are virtually useless, except as bling. The hinges are not necessary, but they got bigger and fancier with every "upgrade".

Besides that, there's no metallurgical benefit from putting brass or copper on steel, it just makes for more rust on the steel. An equal thickness steel hinge, as surely the Romans new, is stronger than brass, but if the brass is strong enough, they probably used it because it's easier to work, and looks "better". If it were only about practicality, plain, rectangular hinges punched out of scrap lorica girdle straps would be perfectly functional. Boring, but probably better in the end. We know they liked shiny brass, because that's what they used.