Based on earthenware excavated at the same time and the conditions of geological formation, it is considered that mokkan was made around the time when the early Naniwa no Miya was completed and it was the finding which urged reconsideration of the existing belief that Manyo-gana came into existence between 672 and 697.
一緒に出土した土器や地層の状況から前期・難波宮の完成前後のものと考えられ、万葉仮名は天武・持統朝（672年-697年）に成立したと考える説に再考を促す発見であった。