Chest of Heirlooms
The Chest Of Heirlooms is a locked container that was obtained during the Treasures of Tokuno events. It is classified as a Minor Tokuno Artifact.
An exception to this rule is the Chest; if unlocked it cannot be turned in. The items inside are typically of low value.
Whenever the events are active, the Minor Artifacts can be obtained by slaying creatures around the Tokuno Islands (with the exception of Cranes). The more creatures killed, the more likely an artifact would appear in your pack upon defeating the next foe.
If you have 10 such Minor Tokuno Artifacts, they can be "returned" to Ihara Soko the Imperial Minister of Trade in exchange for a Major Tokuno Artifact (even if they have been damaged through use).