While on my 2nd account tonight I was perusing my incomplete WvW reward tracks and when I hovered over Silverwastes Reward Track, the final chest was the Warclaw Armor Box!
BTW that account doesn't have POF. Anyway, for the sake of SCIENCE I burned through a few dozen reward potions to get the final chest, and it does indeed give the Warclaw Helmet. Even though I can't do anything with it until I upgrade my account, I'm passing along the info.
WvW™ - where you find more Red Rings of Death than an Xbox repair facility.