017 Seiko ‘Grandfather Tuna’ 6159-7010 from April 1976


Seiko ‘Grandfather Tuna’ 6159-7010



Made for only a short time between 1975/78, the 6159-7010 was Seiko’s answer to the problem of helium ingression into watches during saturation dive decompression. Although only produced for less than 3 years, the design has remained a major part of Seiko’s product line and versions of it are still made today over 40 years later, the popularity of these later versions has fuelled the collectability of the original. Rolex and other brands sought to alleviate the helium gas problem by building helium escape valves into their watches. Seiko took a much more difficult route and chose to build a watch which was completely impervious to helium, so if the gas couldn’t get in….it didn’t need to get out.

Seiko accomplished this by using a one piece titanium case and newly designed gaskets which protected the case/crystal interface. The bezel had quite definite clicks at each of the 60 minutes, it rotated in both directions but was protected from accidental rotation by the external ‘shroud’ which covered over 50% of the bezel. The shroud was also made of titanium but has a matt black ceramic coating, it is held in place by 4 steel allen screws, which add to the industrial/tool appearance of the watch.

The matt black dial is designed with legibility in mind above all else; the tritium indices are huge and surrounded by painted white circles to make them even more visible. There is a large inverted triangle at 12 and large tritium dots for the remainder, the 6 & 9 indices and the 12 have white lines radiating inwards from their edge, giving a sniper scope look & there is a date window at 3.

The movement is the 6159B, which is a high beat (36,000bph) automatic calibre with 25 jewels and is essentially a 61GS movement without the fine finishing and with stronger components needed to drive the larger hands. It has both hacking and quick set facilities and has proved to be an exceptionally robust movement.

Dial is 9+%, case is 95% whilst the movement is 95%.
Diameter 50.5mm; Lug to Lug 52.5mm; Height 18.8mm., it takes a 22mm strap and a new rubber strap is fitted.


£3.000.00 (approx $4,250.00 US)