This bronze mirror was found in the ‘mirror-pool’ at the shrine on Mount Haguro, where it was thrown, along with hundreds of other mirrors, as an offering. The back is decorated with two dancing cranes - symbols of long life and marital fidelity in Japan. The other side is undecorated and was polished to create a reflective surface. Mirrors were first imported from China in AD 300. They were associated with the sun-goddess Amaterasu, ancestress of the Japanese emperors, because of their ability to reflect light.
What was Japan like when the mirror was made?
For many centuries Japan was influenced by China. Then, in AD 894, the Heian emperor took the momentous decision to cease contact with China. For the next three centuries Japanese culture developed in isolation. The Heian court during this period became renowned for its style and aestheticism. Courtiers communicated by writing poetry and held incense fragrance contests. It was during this period that the Tale of Genji was written, arguably the world’s first novel.
http://www.bbc.co.uk/ahistoryoftheworld/objects/81fJfecfSFea12920ZIfAw