This chest is one of two ways to get Ring or Wall spell scrolls - see Feruza ibn Salaq for information on the other method.
Burden used to be an indication of the presence of a rare scroll, but is no longer due to the addition of the weapon.
Similar Chests in dungeon fixed locations drop low level loot. See Sturdy Iron Chest for more information.
The steel chest has a unique treasure profile and generates 1-2 level VII scrolls and a weapon or ball of Coalesced Aetheria in addition to two trophies.