Patch 3.3.0 (08-Dec-2009): Now updates the tooltip on Unbreakable Armor. Tooltip on glyph modified to make its effect more clear as well.
Patch 3.2.2 (2009-09-22): Now increases the armor gained from [Unbreakable Armor] by 20%.
3.1.0 changed Unbreakable Armor to be flat damage reduction based on armor.
Patch 3.1.0 (14-Apr-2009): Additional armor increased to 20%.
Patch 3.0.8 (2009-01-20): Effect changed from "Unbreakable Armor grants an additional 5% parry chance but no longer increases your Strength" to "Unbreakable Armor grants an additional 15% armor".