Seiko 'Grandfather Tuna'

Overall Condition: Good condition overall. Case shows moderate wear. Indices show even patination. Possible service handset.

Seiko's Tuna dive watches are known by the nicknames of "Baby Tuna," "Golden Tuna" and "Grandfather Tuna," but they could also be known as "big," "bigger," and "biggest." But rather than being big simply for the sake of it, the size of the Tunas has functionality at its heart.

Seiko had released its first dive watch in 1965, the Reference 6217 (or 62-MAS). The 62-MAS was water-resistant to 150 meters and had a rotating bezel, luminous hour markers, and a 17-jewel movement (Calibre 6127) with a beat rate of 18,000. It was an excellent effort, competitively-priced compared to Swiss divers, but for Seiko, it was only the beginning.

In 1968, a letter from a disgruntled professional diver in Hiroshima led to a seven year odyssey that resulted in the creation of the Tuna series of dive watches, the first ever designed specifically for saturation diving.

A team of engineers led by Ikuo Tokunaga devised a circular, titanium one-piece or monocoque case with a special "L type" gasket, surrounded by a titanium shroud coated with ceramic. The crystal was held in place with a locking ring. This eliminated the need for a Helium Escape Valve, resulting in a watch that--released in 1975-looked entirely different from any dive watch that had been released.

The Reference 6159-7010 was the first in a lineage of "Tuna" divers with hockeypuck aesthetics built for one purpose: never to fail. Packing 600M of water resistance, the overbuilt dive masterpiece inspired the full lineage of Tuna models which are today some of the most well-regarded in the history of dive watches.

This Reference 6159-7010 "Grandfather Tuna" remains in truly clean condition with a beautifully patinaed tritium dial waiting for its next custodian.