Roman Chain Mail
The Romans got chain mail from the Gauls, but it had been around longer. The oldest example comes from a Scythian tumulus at Zhurovka, dated to the early 5th century BC by the red figure pottery, presumably obtained through trade via Olbia. It is described in the 3rd century BC by Polybius (6.23.15), but only began to be used more regularly in the 2nd century AD.
Very few examples of actual mail survive from either Roman or Celtic graves, which is why the few depictions in Roman sculpture are so interesting.
This fragment was found at the Temple of Bel at Dura Europas (source):
The problem is that excavators later found a whole skeleton wearing mail at Dura Europas (source), but ... he seems to be a Sassanian who died mining under Tower 19 in AD 256 to set off poison gas according to research by Simon James:
What we do have surviving examples of is the fish-scale armour, for example from Trimontium (Newstead):
Chain mail, or lorica hamata, was worn by junior officers and standard bearers primarily in the later Imperial period, and only by those that could afford it during the Republic.