Ports Authority (Nigeria)

The flag of the Ports Authority is green with a white disc in the centre charged with a gold [heraldic] dolphin wearing a naval crown and a chain with a gold hexagram around its neck.
Source: Flags of the World (Barraclough and Crampton) [bcr81] page 153
Santiago Dotor, 13 April 2000

The Nigerian Ports Authority was created in 1955 when it replaced Nigerian Ports and Seaways that had been operated by the Marine Department of the Nigerian Government. The vessels of the Marine Department that had flown the Nigerian Blue Ensign now flew the Nigerian Ports Authority Blue Ensign granted 29 August 1955. The badge in the fly was similar to the badge on the Nigerian Blue Ensign but the circle was white instead of red, and the crown and word NIGERIA in the centre of the star were replaces by the letters NPA in gold. Return of the warrant was requested 6 November 1961, but the ensign was probably not used after October 1960
David Prothero, 13 April 2000