Armor Materials?

From Lords of Men:

Plate and mail is a combination of mail
strengthened with various metal plates.
It gives better overall protection than the
ancient, all-plate harness. Historically, a
few medieval examples of breastplates
(worn over mail) re-appeared by 1200,
but they were not common until about
1300. Plate jambes were added around
1320, and full plate appeared around

Short question: is this a fact? I have a player, who is also an educated historian, who thinks this is false. Are there any historical sources for the appearance of plate and mail in 1200, even the very rare ones?