The Magma Bulwark

This powerful armor offers a protection of 1 AC, due it wasn't "enchanted", it can be weared in conjunction of a Ring of the Princess or such things, it offers the same AC than Full Plate Mail, and it weighs less, but it has lower modifiers.

In-game description
"Forged by the fire giant Varboti as a gift for a Cormyrian general who made peace with his clan, this red-and-black armor lends its wearer a molten aspect while providing protection against almost all but the most powerful blows. Due to its incredibly strong thin material, it also weighs far less than ordinary plate mail."