Bulwark of the Ancient Kings

The Bulwark of the Ancient Kings is the final epic level breastplate that is craftable and wearable only by Blacksmiths with the Armorsmithing specialty.

Source
This item is crafted with Blacksmithing (375); taught once by Armorsmith trainers.

The plans could be learned from the Armorsmith trainers:
 * in Ironforge
 * in Orgrimmar
 * in Shattrath City