Amid the many scandals at the United Nations, a new mystery now looms. What happened to the world organization’s unique and valuable postal archive — in effect, the U.N.’s own stamp collection, one of the crown jewels of its past and a popular point of contact with the global public?

Auditors from the U.N.’s investigative arm, the Office of Internal Oversight Services (OIOS), are currently putting the last touches on an investigative report that has taken months to complete, and that aims to determine exactly what happened — and why — to the U.N.’s rare and much-admired collection of materials that belong to the United Nations Postal Administration.