IDEMITSU KOSAN K.K.

The letters derive from the founder’s name, printed in this note as Idemitso Sazo.

Japanese Shipowners Association material assigns the funnel to Munakata Kaiun. It appears much darker in later references than the earlier pale creamy yellow, a change supported by the JSA chart. A black-and-white photograph of Nissho Maru confirms the funnel arrangement.