Custom brown ink made for Bungubox pen store in Japan. These inks are commonly referred to as Bung Box or Bungbox in the U.S.; each ink is a limited production returning once per year.
2016 autumn, the long-awaited fountain pen from Pelikan, M400 Tortoise Shell Brown was released. The Charm of this fountain pen is the beauty of the brown stripe of exquisite shades made of cellulose acetate.
By all means, please use it for your tortoise shell brown.