National treasure. The dotaku unearthed from the Kamo Iwakura site have a nested structure. In this way, this dotaku was set into No. 1 dotaku. It was made from the same mold as bronze bell No. 7, No. 19, and No. 22 from the Kamo-Iwakura site, and Oda-Kuroda dotaku in Wakayama prefecture.