Deep in the pit, liberated from its tomb beneath a thick slab of concrete, lay a mud-colored mummy. It was discovered near the shrine to a Shiite saint, Shah Abdol Azim, where kings and noblemen have been laid to rest. An excavator working nearby suddenly fell silent, and workers could be heard crying out in amazement.

Had this been Cairo, it would hardly have merited a mention in the local news media. But while Egypt is known for its mummies, Iran certainly is not. Here, the dead are buried in loose white cloth, and the bodies quickly decompose.

The operator of the excavator snapped a selfie with the mummified corpse last month and posted it on social media, where it spawned an enticing theory that spread widely: The remains must be those of Reza Shah Pahlavi, the Cossack Brigade officer whom the British helped install as shah in 1925, beginning a family dynasty that lasted 54 years.