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
1360.

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?

Eirik