This papercraft is Skeleton Key, an unbreakable lockpick found in the game The Elder Scrolls V: Skyrim, the paper model is created by ZombieGrimm. This artifact is one of the Daedric Prince Nocturnal's most revered artifacts, the other being her cowl.
The Skeleton Key can be used like a regular lockpick and can be kept indefinitely, provided it's never returned to the Twilight Sepulcher. In addition, the Lockpicking skill will still increase when a lock is opened. Keeping the key effectively renders the Lockpicking perk Unbreakable entirely obsolete, as well as most of that skill tree.
It can be obtained from Mercer Frey at the end of the Thieves Guild quest Blindsighted. In order to complete the remaining quests for the Guild, the Skeleton Key must be returned in the Twilight Sepulcher. [Source: wikia]
You can download the papercraft model here: The Elder Scrolls V: Skyrim - Skeleton Key Free Papercraft Download