In Wrath of the Lich King it is item level 251 and requires level 80. In MoP Classic it is item level 251, requires level 80 and sells to vendors for 1c.
In the Appearances collection, Relentless Gladiator's Leather Tunic is listed as Vendor. Appearance ID: 10726. No other item uses this appearance, so it is unique to Relentless Gladiator's Leather Tunic.
Read from the World of Warcraft client build files.
How Relentless Gladiator's Leather Tunic Compares
Who It Suits
Leather is the armor type Demon Hunter, Druid, Monk and Rogue wear. With Agility or Intellect, Relentless Gladiator's Leather Tunic suits Assassination, Outlaw and Subtlety Rogue; Brewmaster, Mistweaver and Windwalker Monk; Balance, Feral, Guardian and Restoration Druid; Havoc, Vengeance and Devourer Demon Hunter.
Similar Items
The 10 items nearest to Relentless Gladiator's Leather Tunic (item level 35) in item level among Armor > Leather, Chest slot, from item level 31 to 39.
Items Numbered Next to Relentless Gladiator's Leather Tunic
Blizzard numbers items as they are created, so the named items next to ID 41651 (41646 to 41658) were usually added in the same batch as Relentless Gladiator's Leather Tunic: the same quest line, zone, vendor or reward set.