In Wrath of the Lich King it is item level 226, requires level 80 and is named Dreadnaught Legguards. In MoP Classic it is item level 213 and requires level 80.
Read from the World of Warcraft client build files (JournalEncounterItem, JournalEncounterCreature, Achievement) and the Blizzard Game Data quest API.
How Valorous Dreadnaught Legguards Compares
Who It Suits
Plate is the armor type Death Knight, Paladin and Warrior wear. With Strength or Intellect, Valorous Dreadnaught Legguards suits Arms, Fury and Protection Warrior; Holy, Protection and Retribution Paladin; Blood, Frost and Unholy Death Knight.
Transmog Sets
Valorous Dreadnaught Legguards is part of the transmog set Valorous Dreadnaught Battlegear (Warrior only). The other 16 pieces:
Items Numbered Next to Valorous Dreadnaught Legguards
Blizzard numbers items as they are created, so the named items next to ID 40547 (40541 to 40552) were usually added in the same batch as Valorous Dreadnaught Legguards: the same quest line, zone, vendor or reward set.