• Silverwing Battle Tabard
• Item Level 20Disenchants into:
  Not disenchantable
• Binds when picked up
• Unique
• Tabard
• 
• Vendor 12000

Source

This item is a PvP reward, and can be purchased for 2,059 from Illiyana Moonblaze <Silverwing Supply Officer> in Ashenvale Forest.

Patch changes

• Patch 3.3.3 (2010-03-23): No longer requires Warsong Gulch Marks of Honor to purchase. 
  
• / Patch 2.0.1 (05-Dec-2006): Reputation requirement removed. 
  
• Patch 1.6.0 (12-Jul-2005): Added. 
  

External links

• Battle.net (EU)
• Wowhead
• Thottbot
• WoWDB