6306

Production Info

  • Production: 1976 - 1981
  • Movement: cal. 6306
  • Description: 150m divers

Technical Manuals

Models

  • 6306-7000
  • 6306-7001

Details

The cousin of the 6309, the 6306 is a 150m diver that looks and feels identical to the cushion-cased 6309, but was marketed only in Japan and uses the cal. 6306 movement.

The cal. 6306 movement has 21J and runs at 21,600 bph. It hacks and has a quickset day/date calendar mechanism with a Japanese/English day wheel.

The 6306 divers are much rarer to find than the 6309s because their production years were relatively short and they were Japan-only models that use a 21J hackable movement (compared to the 17J non-hacking movements in the 6309s). Like the 6309, the 6306 diver has a bi-directional non-locking bezel.

According to Mr. Ikuo Tokunaga, the designer of many of Seiko's diver watches, the 6306 diver was put into production slightly before its brother the 6309. The 6306 diver differs from the 6309 in that the cal. 6306 movement has 21J (as supposed to its base caliber 6309's 17J) and it has a Japanese/English day wheel. A promotional pic of the 6306 diver from an early Seiko catalog is here.

Mr. Tokunaga describes the design of the 6306 and 6309 divers in the following message:

I designed these models from 1975, as the next model of 6159 600m professional diver's watch. So if I am allowed to judge this history from my memory and my saved stuff, it will be as follows.

Both of the 6306 diver's watches for domestic and the 6309 diver's watches for overseas were made in Suwa Seikosha from 1976, and 6306 diver's watches were put on the production "slightly first". Those basic specifications were same except for the number of jewels and the bilingual language display of the calendar.

The reason why I said the "slightly first" is only that I was not able to confirm the start month on the production. I am sure the 6306 diver's watches came first, too.

If speaking from the viewpoint of plans or of technical designing on 6306/6309 diver's series, I am sure the concept of influence or of derivation between those watches did not exist in 1976. It is because I issued the specification drawing of those diver's watches as the same one. This means that I wrote only a description such as "6306 ( Japan ) / 6309 ( Overseas )" on one sheet of common paper in order to show the difference. The drawing below is the original specification drawing of 6306/6309 150m diver's watch (which has been editted).

Incidentally, as for those calibers, the 6309 caliber was designed first. The base caliber of 63 series (about ten) is 6309.

Ikuo Tokunaga

6306 Diver in the Field

The Hokinkee article "Found: A Seiko 6306 From A 1979 Antarctic Research Expedition" recounts how a collector had bought a special 6306 diver through an Ebay sale, and through some detective work discovered that the watch had a connection to the 1979 Japan Antarctic Research Expedition. This is in line with the history of the JARE research teams using Seiko divers as part of their field equipment.

Credit: Hodinkee

The inscription on the watch dial -- MSST1979-80 -- indicates that the diver was likely used by someone in the research team associated with the McMurdo Sound Sediment and Tectonic Study (MSSTs):

The [MSST] project kicked off with the first coring on October 21, 1979, with the objective of drilling into McMurdo Sound to retrieve sediment samples which would be able to tell us more about the history of Antarctica, particularly a key period between 50-10 million years ago, during which ice gradually covered the continent.

Dr. Tetsuya Torii, ... a renowned Antarctic scientist ... had by the end of his career visited Antarctica twenty six times over twenty seven years.... He was one of three geochemists on the McMurdo Sound Sediment and Tectonic Study in 1979, and he gifted watches to the group of scientists from around the world that took part. It was one of those very watches gifted by Dr. Torii to one of his colleagues that turned up on eBay last June.

The article is an interesting read as it illustrates how an old, scratched up vintage watch that shows up in a sale can contain a mysterious detail that, once you follow the trail, leads to a thread that opens up a fascinating history of adventure.

More info