Yakoogai, green turban shell (No.12 Large)/夜光貝NO.12Ｌ
Turban shell for mother-of-pearl inlay.
It has several layers inside, starting with a blue-green and moving inward to the nacreous. The blue-green coloration depends on the individual but ranges from a bright turquoise blue to a deep forest green.
The size can be slightly different as it is natural materials.