These mirrors were dedicated to Hôryû-ji Temple by Empress Kômyô (701-760) on the anniversary of the death of Prince Shôtoku (574-622), on the twenty-second day of the second month of Tempyô 8 (736). Cast in nickel, which contains a relatively large amount of tin, these large mirrors are harder and whiter than those made of the more usual bronze. Gamma-ray fluoroscopy of both mirrors shows that they were cast using a superior technique that resulted in a good flow of molten metal.
The diameters of these pieces vary slightly but the patterns on the obverse, with the exception of the wave pattern surrounding the central boss, closely resemble each other and are of Chinese style. Four forested mountain peaks, bearing lions, deer, birds and a seated figure, are arranged in the four directions around the circumference of each mirror. These islands are surrounded by waves, upon which float two fishermen in small boats.
It is unclear whether these mirrors were made from the same mold or cast from separate molds. Their place of production is also uncertain although it is thought that they may be "imitation mirrors" (J. bôseikyô), cast in Japan but copying the style of Chinese mirrors.