Seiko dive Calibre 6309

Calibre 6309
Seiko 6309-7040 (diganti dials+hand pakai 6105)
Caseback tertera 4DO494, artinya jam ini dibuat = Desember 1984

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Models with big cushion cases:
6309-7040 (all have big cushion cases and black bezels, though some have seen
6309-704X divers with blue-and-red bezels)
6309-7049

Models with slimmed-down case:
6309-7290 (start of the use of slimmed-down cases, black-bezel version)
6309-7290 with "17 JEWELS" on dial (Japan-made version, with black bezel)
6309-729A (identical to 6309-7290 except with blue and red bezel)
6309-729A with "17 JEWELS" on dial (Japan-made version, with blue and red bezel)
6309-729B? (very rare model, with slimmed-down case and orange dial)


Details:

The 6309 divers replaced the 6105 as the standard models of 150m divers. The 6309s were marketed outside of Japan while a version using the 6306 movement was sold only in Japan (but for a relatively short 5 years).

The cal. 6309 movement is a successor of the 6105. It has 17J and runs at 21,600 bph. It's non-hacking and has a quickset day/date calendar mechanism.

Like the 6105, there are 2 series of 6309 divers. The earlier versions -- 6309-7040 and 6309-7049 -- are housed in big cushion cases and have round markers. The later versions -- 6309-7290 and 6309-729A/729B -- have slimmed-down cases and rectangular markers (which make them very similar to the current SKX007/173 models). While the earlier 6105 divers used the "turn and lock" crowns, the 6309 crowns are all screw-down. The 6309 divers seem to all have bi-directional non-locking bezels.

Some people have asked how the 6309-7049 and 6309-7040 differ. The consensus among S&C Forum collectors is that there's no difference between the 6309-7040 and 6309-7049 models. John Davis/ei8hthoms explained that the last digit of the case number indicates a regional code used for marketing (9 means N. America and 0 means elsewhere).

Mr. Tokunaga, the designer of many of Seiko's diver watches, has provided some valuable historical info about the 6309/6306 divers here. The 6309 and its brother the 6306 were both put into production in 1976 -- the cal. 6309 movement was designed first (and serves as the base caliber for the 63 series of movements), but the 6306 diver was put into production "slightly first," before the 6309. He also included a scan of the original specification drawing for the 6309/6306 divers as well as promotional pics of the 6309 and 6306 watches from early Seiko catalogs.

For a comparison of the details of the 6309-7040 and 6309-729A with lots of pics, check out Mark Skorji's post here.

There are many anecdotes of folks who have put their 6309s to the torture test.

NDT34321 writes:

I've come out of lurking mode to present my version of an extreme torture test on the 6309-7049 150mm diver... this watch spent over 1100 hours underwater...I was a contract diver who worn the Sekio as a good luck piece....not a part of my working system....I had made a 4" rubber band cover out of a leg tourniquet to fit over the watch...pipelay barge or dredge or jet barge divers and Non Destructive Testng divers don't wear watches....strange?...Not really..the limited visiablity conditions where my type of diving takes place were river bottoms and mid harbors(the sekio was there)in 76 Boston Harbor USA had 12' of overburden above harbor floor(the 6309 was there)...biopsy (coreing sampling) a bridge spanning the Mississippi.. easy current.. no visibility (the sekio was there)torque valve on the hydraulic machine slammed my wrist into a piling...(the seiko was there)I add that I did wear a 50cm depth gauge at all times..the incident broke a bone in my wrist it moved the bezel to one side..new bezel and crystal... the watch was find... destroyed my GG..the Seiko had 5 years of this real time torture test... I also played in my Sekio..this was a 24hr watch...the watch has been restored now by IWW... Jack related not a spect of rust on the movement... it is still my everyday watch though its diving days are over...so when a watch is nominated as one of the most robust and enduring divers... with a strong record to prove by....I believe my unintentional real life torture test on my 6309 speaks well of the watch.
The 6309 divers (like the 6105s before them) were extremely popular among the military. Read the annecdotes here: "17 Year Long Torture Test, Seiko 6309."

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Question:

Dear Tokunaga-san

I woudl like to know what years the 6306-7000/7001 diver was produced, and how that affected the 6309-7040/7049 diver. Where both watches bbeing produced durring the same years, and which one came first, the 6306, or the 6309.

I have always though the 6306 21 jewel came first, but I seek your advise on this.

Thank you.
Randall Benson
2manywatches

Reply:

Dear Randall-san:

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.

I hope this helps you.
Sincerely yours,
Ikuo Tokunaga

Source:
http://www.makedostudio.com/watches/seiko-divers/

https://archives.makedostudio.com/seiko-divers/index.html