Compared with high-quality coins issued during the era of the Northern Sung Dynasty, such as Kaigen-tsuho during the Tang Dynasty, they were as small as the present five-yen coin, with some of them as thin as an eggshell, and were made unevenly.
唐の開元通宝など北宋までの良貨（精銭）に比べ5円玉程度と小さく、卵の殻のように極めて薄いものもあった。