The armor stats are identical to those of the Demonspike Coat - a unique Full Plate Mail in Diablo I.
The characteristics of this armor are very powerful, but the armor is unusable for the player character. As a result, it's only an easter egg. If you wear it through cheating, it will take away all your Agility.
The jacket doesn't have a ground frame. Therefore, when dropped from the inventory, it appears as large on the ground as it does in the inventory.