Affordable Vintage: Seiko 6309

There are many vintage Seiko diver models that are popular with collectors, but none more so than the venerable 6309-7040/9. Generally regarded as the their third generation professional/recreational diver, the 6309-704X replaced the 6105 series in 1976 and continued to be produced until 1988. As with many of the vintage Seiko models, the last digit of the reference number denotes the original market that the watch was intended for. The 7049 was designated for the North American market, and the 7040 was for the Japanese Domestic market and the rest of the world. While there are some later models that started with 6309, for brevity’s sake I’ll just use ‘6309’ in this article to refer to the 6309-7040 / 6309-7049. It should be noted that from 1976 to 1981 Seiko produced the 6306-7000, a cousin to the 6309. It’s nearly identical to the 6309, except it has a 6306 hacking movement and it has a Kanji day wheel. The 6306 was made exclusively for the Japanese domestic market.

The Seiko 6309 comes housed in a large cushion shaped stainless steel case that measures 45mm wide by 48mm long and 13mm thick, with nice 22mm lugs. Even though this is a large watch, the design wears extremely comfortably, and is and continues to be a favorite among Seiko collectors. The original factory case finish features circular brushing on the top, with polished sides and straight brushing on the bottom. There is a nice, elegant sharp line delineating the top brushed portion from the polished sides. The oversized crown is located at 4 o’clock and is recessed into the case for protection. One of the best features of the 6309 is the crown, which screws down securely for superior water resistance. This is in contrast to the prior 6105 models that did not screw down. The crown is attached via a two-piece spring-loaded stem that makes the crown pop out a bit after unscrewing it. It should be noted that the crown tube is not replaceable, so if it is stripped, it’s nearly impossible to be fixed.

The bi-directional 60-click bezel features a matte finish black aluminum insert that angles slightly downward towards the crystal from the outside edge. The outside of the bezel has two rows of deep knurled grooves for a superior grip. The crystal is made of Seiko’s proprietary Hardlex mineral glass, and is flat with a frosted edge. It rests on an “L” shaped gasket and is held securely in place by a metal retaining ring that is hidden under the bezel.

The dial is flat black, with large lumed hour markers. The 12, 6, and 9 makers are larger trapezoid shapes, the 12 being a split design, and the others are round. A large day/date window is at 3 o’clock. This is a classic Seiko design, and variations on this continue to be used to this day. The dial is signed “Seiko, automatic” under the 12, and “Water 150m Resist” above the six. The “Water” and “Resist” are in red, and the “150m” is in silver.

There are two main dial variants, the “Suwa dial” and the “non-Suwa dial”. This refers to the use of the Suwa stylized “S” symbol that was used to designate that a watch was made at the Seiko Suwa factory in Japan. The Suwa dial was used from 1976 to about 1980, and has the Suwa symbol just below the “Water 150m Resist” text. It also has the text “Japan 6309-704L T” along the bottom edge of the dial. The date window has a deep bevel around it on this one, and the case back will have “Japan A” on it.

The non-Suwa dial was used between 1980 and 1988, and is essentially the same except it does not have the symbol above the 6. In addition, the text at the bottom edge reads “6309-704X T (small Suwa symbol) MOVT AND DIAL JAPAN CASED HONG KONG”. In addition, the date window has a noticeably shallower bevel. There are other subtle variations, on these dials, but these two are the most common variants.

There are tons of fake (aka aftermarket) dials out there, so it’s important to do know what the reals ones look like. One of the easiest things to look for in a fake dial is a date window with no bevel (these are usually made to look like a Suwa dial, so the lack of bevel on the date window is pretty obvious). Another characteristic of most fake dials is that the 6 o’clock hour marker will extend down into the area at the bottom edge where the small writing is. On legitimate dials the maker is clearly above the writing.

The hands on the 6309 are quintessential Seiko, and they have continued to use variations on these hands to this day. They are large with large lume plots, and the minute hand has a big arrowhead at the tip. The second hand has a large lume filled ‘lollipop’ for easy reading. They are polished steel that is quite flat with nice sharp edges. Again, aftermarket hands are everywhere, and are usually fairly easy to distinguish from the originals in that they have a more rounded edge to them and appear more ‘3D’.

The Seiko caliber 6309 movement is a 17 jewel automatic, and is a true workhorse. There are many stories and examples of people acquiring a 6309 that is 30+ years old that have never been serviced and yet continue to work perfectly with a strong power reserve and keeping excellent time. It’s a true tribute to the folks who designed these movements. The 6309 is automatic, but does not hand wind or hack. Like most Seikos, the day/date has a quickset mechanism used by pulling the crown out one notch and turning it one way to advance the day, and the other way to advance the date.

This diver originally came supplied only with a rubber strap, the Seiko GL831. It is a long, semi-hard rubber/plastic strap that has accordion folds on both sides, along with a nice big steel tang buckle. This strap design has been used with variations continuously up to today with the Z22 strap. Personally I don’t find it to be that comfortable, as they tend to be a bit stiff. Fortunately, with 22mm lugs, the 6309 has nearly limitless strap options, and looks great on just about everything from Isofranes, to shark mesh, to thick leather straps.

The 6309 is one of those watches that didn’t really do it for me for quite some time. I’d seen many, many pictures posted on forums from happy owners, but it really didn’t resonate. Eventually I decided to get one and see what all the fuss was about. Well, once it was on my wrist I was hooked. The large cushion case is very comfortable, and wears well for a large watch. It is large, especially for a vintage watch, but not overly so like many of today’s modern behemoths.

The build quality is immediately evident, from the brilliant case finishing to the firm ‘click’ of the bezel. The large luminescent hour makers and hands make it very easy to read, and the style of the dial and hands just screams “Seiko”. The movement, while simple in it’s finishing, is robust and dependable, and the quickset day/date makes it a snap to set. The efficiency of the automatic winding mechanism is amazing, one light shake and the second hand starts ticking right away. One of the best features of this vintage diver is its screw down crown and replaceable gaskets, making for excellent water resistance. These watches are easily restored to original depth ratings, and I know many people who wear their 6309 in the water on a regular basis.

Like the 6105 before it, the 6309 has also shown up in pop culture. Ed Harris wore a 6309 in the film “The Abyss”, and Mick Jagger has also been photographed wearing a 6309. The 6309 is immensely popular with Seiko collectors, and while it is (in my opinion) currently grossly undervalued, it is gaining in popularity and garnering more respect in the vintage watch community as well. While it is by no means a scarce watch, they are getting increasingly more difficult to find in good, original condition.

These watches were more often than not used as they were intended, as a tool watch for diving. As such, they are often found with signs of wear consistent with heavy use and exposure to water and humid climates. Use of aftermarket parts and ‘mods’ are also very common, making all-original examples harder to come by. With some patience and knowledge, nice examples of unmolested 6309’s can still be obtained, and I’ve found the prices to range from $250 up to $500+ for a mint example. There really is no better “bang for your buck” in the vintage dive-watch-world, in my opinion!