This iron mirror bears the images of five auspicious animals inlaid with gold filigree. Cao Cao recorded in his Miscellaneous Imperial Household Articles that the emperor used 1 piece of 1.2 chi (a chi is a traditional Chinese unit of length about 0.33 meter) gold-inlaid iron mirror, the empress and crown prince used 4 pieces silver-inlaid iron mirrors. The technique of making iron mirrors with gold or silver inlays did not developed until the end of the Han Dynasty.