In Wrath of the Lich King it is item level 200 and requires level 80. In MoP Classic it is item level 200, requires level 80 and sells to vendors for 1c.
Read from the World of Warcraft client build files.
How Hateful Gladiator's Scaled Helm Compares
Who It Suits
Plate is the armor type Death Knight, Paladin and Warrior wear. With Strength or Intellect, Hateful Gladiator's Scaled Helm suits Arms, Fury and Protection Warrior; Holy, Protection and Retribution Paladin; Blood, Frost and Unholy Death Knight.
Transmog Sets
Hateful Gladiator's Scaled Helm is part of the transmog set Hateful Gladiator's Scaled Armor (Paladin only). The other 16 pieces:
Items Numbered Next to Hateful Gladiator's Scaled Helm
Blizzard numbers items as they are created, so the named items next to ID 40821 (40816 to 40826) were usually added in the same batch as Hateful Gladiator's Scaled Helm: the same quest line, zone, vendor or reward set.