A Titanium Professional 600 dive watch, Seiko. Circa 1975-1979. Reference 6159-7010. 51 mm case in titanium and PVD coated titanium outer, mechanical self-winding movement. Black dial with luminous hour markers and hands. On original hardened rubber divers strap. Dial and case signed. These are also known by collectors as 'Grandfather Tuna' as they have the side profile of a tuna can. This was the first of its kind developed by Seiko in the 1970's.