|These are often passed off as the Three Sacred Treasures,|
the Imperial Regalia of Japan, but they are a collection
of items brought together to represent the Three. The Three
have never been so blatantly exposed to the public eye.
The Three had been used since at least 690 CE for investing the Japanese emperor with the symbols of his authority. They came to represent three virtues: valor (the sword), wisdom (the mirror), and benevolence (the jewel). They continue to be treated that way, although they are not part of a public ceremony: the emperor is invested with these privately, and no definitive pictures exist of the items. The jewel and sword were used in 1989 and 1993 in the ceremony for Emperor Akihito, but they were wrapped and not seen.
They are a symbol of the divinity of the emperor, because they were not made on earth; rather, they were sent here by Amaterasu, the goddess of the sun, with her grandson Ninigi-no-Mikoto, who united Japan and founded the Japanese line of emperors. Unfortunately, the uniting of Japan was not constant. In 1183, the Minamoto clan fought the Taira clan. The Taira clan and Emperor Antoku fled with the Three Sacred Treasures. And then this happened...
Emperor Antoku was only eight years old. His grandmother, as his guardian, tried to prevent capture by throwing herself, and the emperor, and the sword and jewel into the sea. Divers found the jewel, but not the sword. The mirror was captured, but the story goes that a soldier who opened its box was struck blind.
With the loss of the sword, how would any emperor be properly invested? That's when the stories start: that a replica was made, or that the original is in the hands of the authorities, and it was a replica that was thrown into the sea. Perhaps this is why the regalia were shrouded when used for Akihito's ceremony.
Whether what exists is truly the original set is immaterial to historians. During the 14th century, Japan was divided into a Northern and a Southern Dynasty, with each dynasty claiming an emperor. Since the Southern Dynasty possessed what was claimed to be the Three Sacred Treasures, historians award them the legitimacy of government, and count those emperors as the "real" emperors.