It was common that mirrors were made from bronze in ancient times and were rarely made from steel. Among these rare steel mirrors, this mirror is particularly exceptional and rare, despite its rusted condition, with gold and silver lines and precious stones such as Turkish stones inlaid in the steel face.
This mirror was said to have been accidentally unearthed in 1933 (the 8th year of the Showa era) during the construction of the national Kyûdai main railway route. While the exact location of its excavation is unknown, it can be said that it was discovered together with the excavation of an ancient tumulus or horizontal hollow tomb.
The central knob is in the shape of a semi-circle and inlaid with gold lines. Around the knob there is a flying bat pattern emerging from a four-leaf clover motif, with the flying bat pattern lined in gold and silver lines. There is also a curling cloud pattern lined with gold and silver lines, with a glass ball set in the center. Within the flying bat pattern are the characters "長," "宜," "…" and "孫" engraved in gold. The unclear character is considered to be "子." Around the central knob, there are tiny dragons inlaid with gold, with the eyes and the body segments in Turkish or red gems. The rim has a curling cloud pattern lined with gold. Such an exquisitely ornate mirror is extremely rare and it shows the high quality of craftsmanship of the time.
It is considered that this mirror was made in 2nd – 3rd century in China. While it is unclear when the mirror was brought to Japan, it is felt that it was passed on from one generation to the next and eventually buried together with its owner around the 6th century. It is of great interest what kind of person the owner was able to obtain this mirror – considered one of the finest in China – and be buried with it.