This is an 18 guage steel, full size, fully wearable, shoulder guard.
A pauldron (sometimes spelled pouldron or powldron) is a component of plate armour, which evolved from spaulders in the 15th century. As with spaulders, pauldrons cover the shoulder area. Pauldrons tend to be larger than spaulders, covering the armpit, and sometimes parts of the back and chest. A pauldron typically consists of a single large dome-shaped piece to cover the shoulder (the "cop") with multiple lames attached to it to defend the arm and upper shoulder. On armour designed for mounted knights, whether in the tournament or the field, the pauldrons would usually be asymmetrical, with one pauldron sporting a cut-away to make room for a lance rest.