On the back side, a hallmark consisting of three characters is carved and the hallmark is one of the following four combinations: '弥・七・九' (ya, seven, nine), '次・七・九' (nami, seven, nine), '坂・七・九' (saka, seven, nine), and '弥・七・新' (ya, seven, shin).
裏面に「弥・七・九」、「次・七・九」、「坂・七・九」、「弥・七・新」のいずれかの極印が打たれている。