Lorica Hamata or Roman chain mail is one the three major types of armor used by the Romans. Chain mail has always been thought of as a very high quality armor due to a number of factors. It affords great protection for its weight, it is constantly moving so the rings stay clear of rust, and it affords the wearer a great deal of mobility. Although we don't have evidence of the armor being used before Rome's conquest of Hispania, it's commonly thought that the Romans learned about it's existence from wars with the Celts.
The armor required about 30,000 7mm rings to make one suit of armor. The armor also included a pair of very dashing shoulders that ran from mid back to the torso. The Romans first started using this metal lifesaver in the 1st century BC and it never really went out of style even when more advanced armors were invented.