5th Century or so A.D.

[atgxtg]

I also have a couple of books that suggest the celts invented chainmail armour - examples have definitely been found in archaeological digs if the museum exhibits I've seen are to be believed.

I have the same info.

As do I; it is not, however, the normative armor of the celts, especially the western celts (iberia and britain). I'm not certain about the bce gauls; I've not been looking at their stuff.

Also, mail may not be a single invention item, since it arises in the orient as well.

Yeah, it looks like several cultures invented it independently. Probably because the idea is intuitive, once you can work the metal.