The Black Prince by Submarine Products Ltd.  This was yet another very hard breathing regulator from the Submarine Products Company.  It did however have a high pressure port for a contents gauge.  The thread is the same as those on the Heinke and Siebe Gorman regulators.  This regulator was showcased in the British diving magazine, Triton in the February 1971 issue on page 40.  It was advertised as having unbreakable delrin, and sold for 16 pounds and 16 shillings.     If you have any more information on this reg please contact The Scuba Museum.