Read from the World of Warcraft client build files.
How Taskmaster's Mining Cap Compares
Who It Suits
Leather is the armor type Demon Hunter, Druid, Monk and Rogue wear. With Agility or Intellect, Taskmaster's Mining Cap suits Assassination, Outlaw and Subtlety Rogue; Brewmaster, Mistweaver and Windwalker Monk; Balance, Feral, Guardian and Restoration Druid; Havoc, Vengeance and Devourer Demon Hunter.
Transmog Sets
Taskmaster's Mining Cap is part of the transmog set Khaz Algar Trophymaster's Leather Armor (Rogue, Monk, Druid and Demon Hunter only). The other 16 pieces:
Blizzard numbers items as they are created, so the named items next to ID 221215 (221210 to 221220) were usually added in the same batch as Taskmaster's Mining Cap: the same quest line, zone, vendor or reward set.