Lorica Segmentata

Lorica Segmentata was a type of Roman Armour consisting of overlapping curved strips of iron, attached to leather strips. It was worn by the Roman Legionaries from 9 BCE until the end of the third century CE.
During this time the Roman Auxiliaries wore chainmail known as Lorica Hamata.

They were formed into two halves, forming a front and rear section around the body, which were then attached together. Two sets of shoulder guards protected the upper body. The iron was hardened into steel on the outer surface, giving it great strength.
It separated into four separate sections, each one folded down on itself, and could then be packed into a very small space.
It was faster and cheaper to manufacture than the thousands of iron rings required for Roman Chainmail, Lorica Hamata.

It was only in use by the Roman Auxiliaries between 9 BCE until the end of the third century CE.
During this time the Roman Auxilia wore Lorica Hamata Chainmail.

Chainmail was used by the Legionaries of the Roman Republic and early Empire until 9 BCE. Then Chainmail was used by the Auxilia. After the third century, the Roman Legionaries returned to using Lorica Hamata.