High Steel Gunblade

High Steel Gunblade is a Gunbreaker's Arm.

Source
High Steel Gunblades can be crafted or obtained as a quest reward.

Crafting
High Steel Gunblades can be crafted by blacksmiths as a level 61 recipe with the following materials:
 * x2
 * x1
 * x1
 * x3
 * x2

Quests
High Steel Gunblades can be obtained as a reward from the following quest:
 * The Makings of a Gunbreaker