If the Bible account can be taken as accurate, It'd probably been somewhere around ~700 B.C

Goliath would almost certainly have worn bronze scale. Scale armour was the only form of metallic armour defense during the time-period in question. Unless Goliath was using Mycenean equipment, there's not much chance he could have had plate elements in his panoply. The only armour that was fashioned from plates during much of the period was helmets.

Maile armour did not exist in this time. It was invented roughly around ~400 B.C in Gaul. It quickly gets into the hands of the Etruscans, and two-and-a-half centuries later Every richman and their mother was wearing maile both in the Mediterranean and Increasingly in the middle east. Unless you're a Roman Legionary of the Marian/Augustan period, Everyone gets that.