Seiko Tuna For The Rest of Us

Sacred ground to geeks, a rathole to others

March 05, 2018

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Sacred ground to geeks, a rathole to others. This Seiko Tuna article is for the rest of us. The hope is to provide insight into the history of all professional Seiko Tuna models. Starting with the 1975 reference 6159-7010 and finishing with the SBBN040 of today.

We’ve probably all heard of the professional diving watches produced by Seiko nicknamed ‘Tuna’. And we might know as well that this wasn’t a given name from its birth. Because of the cylindrical shape of the lugless watch casing, its form resembled a tuna can. It’s been said that the nickname came up years and years ago on one of the then few existing Internet watch forums. I guess it’s clear that the name has not much to do with the Tuna fish species, but more with the tin where they generally end up in.

Meanwhile, the Seiko Tuna nickname beholds a whole universe of different Seiko dive watches. It’s certainly not one watch we’re looking at here, but much more a series. Seiko Tuna is not an official model name, and this is where the fog kicks in, where we no longer see the woods for the trees.

The Grandfather Tuna, the first descendant the Golden Tuna, and the latest off-spring the SBDX014G

A Bit Of Seiko Tuna History

Where to start? Let’s just briefly mention that Seiko has produced watches for divers since 1965. Model 6217-8001, also known as 62MAS, saw the light with a 150M depth rating and a rotating divers bezel as Seiko’s first divers watch. You’ll find Michael Stockton’s article on that watch here. In 1967/8 two updated versions, models 6215-010 and 6159-010, were even able to withstand a 300M water column.

However, just like other manufacturers, Seiko faced trouble when these watches were used professionally for helium saturation diving at great depths. Dive watches blew their glass off during decompression. It pointed out that under high pressures the inert helium gas used could enter the watch through regular gasket constructions. Building up pressure inside the watch, equal to the pressure outside of the watch at that depth. Then, while decompressing the diver, the helium gas couldn’t get out quickly enough, and thus the build-up pressure inside the watch caused the glass to blow off.

Saturation diving explained

The Seiko Solution

At that time some manufacturers looked for a solution to get the pressurized helium out of the watch quickly enough during decompression. Not Seiko. Under the patronage of Ikuo Tokunaga Seiko choose to look for a solution so that the helium couldn’t enter the watch, and no pressure was built up inside. And it was found, Seiko’s solution was found in a special type and construction of the gasket, combined with a titanium monocoque casing. In 1975 it was used for the first time in the Seiko 6159-7010 or model YAQ028.

Mr. Ikuo Tokunaga explaining Seiko Professional divers watches during the 2015 Seiko Media Experience Tour (click here for the full report). And the book (in Japanese language only) he wrote about this matter.

The first Seiko incorporating Seiko’s Tuna design

The Seiko 6159-7010 was a watch with a lot of firsts. It was Seiko’s first watch with a ‘professional’ depth rating of 600M. It was the world’s first diver’s watch with a monocoque titanium case. It was the first watch to feature a two-layer case construction with a titanium shroud coated with ceramic for greater security against shock. A new, accordion-style type of strap was fitted, ensuring ease of use by expanding and contracting as the divers’ depth changed. All in all, over 20 patents were granted to this, at that time, revolutionary timepiece.

The Grandfather Tuna

6159-7010

As mentioned above, the 6159-7010’s cylindrical shape of the lugless watch casing resembled a tuna can. The officially named ‘Professional Diver 600’ would become the ‘Grandfather Tuna’. A watch which we at Fratello Watches all highly respect; Robert-Jan describes the acquisition of his Seiko Tuna 6159-7010 here.

Now we’re getting to the point. We, and the readers this article is aimed to have a starting point. 1975, the very first Seiko Tuna. Implying that there were more to come. And that was what happened.

To determine our starting point somewhat more precisely, I want to specify the main components and specifications of which this first Seiko Tuna was made up from.

reference 6159-7010, model YAQ028, nickname Grandfather Tuna
large monocoque inner casing, made of titanium, blanc steel bezel
51mm cylindrical protective black ceramic coated titanium shroud bolted to the inner casing
hardlex crystal
automatic Seiko 6159, 25 jewels, hi-beat (36.000/h) movement
600M depth rating
polyurethane strap

Important information if you intend to read on

From this point onwards, I won’t go into more or less equal-looking Seiko dive watches which were presented after the ‘Grandfather Tuna’, but with lesser specifications. They understandably might be nicked Tuna as well, but that’s because these watches look equal. Technically they’re not. They don’t use a titanium monocoque casing, and they’re not at least 600M waterproof. I consider them commercial offspring which I don’t include in this write-up. This article is about the – in my opinion – real deal Tuna, without being distracted.

7549-7009 / PYF018

The first descendant, the Golden Tuna

7549-7009

Let’s transfer ourselves to the end of the seventies. Mechanical automatic watch movements had a hard time, while new quartz technology, providing much higher accuracy, was knocking on the door. Switzerland was sleeping and this new technology came from Japan. Not very surprising that, only three years later in 1978, Seiko’s upgrade to their most professional watch was a 5 jewels quartz movement. The caliber number of this quartz movement was 7549 and so the type indication of the first descendant of the Grandfather Tuna became 7549-7009 or model PYF018.

Something else changed as well though. To enhance the surface properties of the watch’s inner titanium case, it was coated with Titanium nitride. Titanium nitride (TiN) is an extremely hard ceramic material and has a golden appearance. Except for the difference in color, the size changed as well; it became approximately 2mm smaller in diameter. The ‘Golden Tuna’ was the next family member, which brings us to the following specifications:

reference 7549-7009, model PYF018, nickname Golden Tuna
large monocoque inner casing, made of TiN coated titanium, steel bezel gold colored
49mm cylindrical protective black ceramic coated titanium shroud bolted to the inner casing
hardlex crystal
quartz Seiko 7549, 5 jewels movement
600M pressure rating
polyurethane strap

Different case backs and inscriptions

The Next Real Offspring

SBDS018

As mentioned, for the sake of clarity and transparency I won’t include all kinds of well-meant similar-looking models with lesser specifications. Therefore it took eight years before the next real offspring was born. Seiko managed to raise the pressure rating of the titanium monocoque ‘Professional Quartz Diver’ even further and came up with a whopping 1000M. And the quartz movement was totally revamped as well and much improved. The new caliber was the 7 jewels 7C46, which made the watch the 7C46-7009 or model SBDS018. Because the looks of the watch didn’t change much, the nickname remained ‘Golden Tuna’ as well. The inner casing was still TiN coated titanium, the shroud black ceramic coated titanium. It’s 1985 and we’re up to the following specifications meanwhile:

SBDS018

reference 7C46-7009, model SBDS018, nickname Golden Tuna
large monocoque inner casing, made of TiN coated titanium, steel bezel gold colored
49mm cylindrical protective black ceramic coated titanium shroud bolted to the inner casing
hardlex crystal
high-quality quartz Seiko 7C46, 7 jewels movement
1000M pressure rating
polyurethane strap

For 13 years or so, it remained relatively quiet in terms of the development of the real deal Seiko Tuna. Of course, some lesser brothers were born while Seiko tried implementing some new techniques in Tuna-like watches. An AGS (later named Kinetic) movement saw the light in 1990, domed glass was implemented on a 300M model, and a Scubapro branded model was presented in 1999.

And Then A Golden-Tuna Re-issue

SSBS018

Then, in 1997 there was a re-issue of the 1000M ‘Golden Tuna’ model. It had reference number 7C46-7008 or model SSBS018. A re-issue should be considered a new version of a more or less same watch. It might be issued with a new reference number because of small technical upgrades or slight aesthetic differences. The differences between the SSBS018 versus the SBDS018 had to be found in the dial, the strap, and the lettering on the case back. All hardly noticeable though, it remained more or less the same watch. Here are its specifications:

SSBS018

reference 7C46-7008, model SSBS018, nickname Golden Tuna
large monocoque inner casing, made of TiN coated titanium, steel bezel gold colored
49mm cylindrical protective black ceramic coated titanium shroud bolted to the inner casing
hardlex crystal
high-quality quartz Seiko 7C46, 7 jewels movement
1000M pressure rating
polyurethane strap

A Limited Edition Homage

SBDX005

One year later in 2000, there was great news. In the ‘Seiko Historical Collection, The Year 2000’ Seiko presented an homage to the original 600M Grandfather Tuna. And in my opinion, it was done quite right. It had a slightly larger diameter of 51mm of the original 6159-7010 again (versus 49mm of later quartz descendants). And there was an automatic movement used again as well. Not exactly the same movement, however, it was replaced by the 8L35. A high-quality automatic caliber derived from Grand Seiko’s 9S55, but lacking its decoration and fine adjustment. Even the golden and/or black touch of the quartz descendants was omitted, the homage had a blanc titanium monocoque casing again.

The reference number of this homage was 8L35-0030, and the model indication was SBDX005. The sad thing was that Seiko only produced 1.000 pieces of them. Here’s the list of specifications:

SBDX005

reference 8L35-0030, model SBDX005, nickname Historical Tuna, 1.000 numbered pcs.
large monocoque inner casing, made of titanium, blanc steel bezel.
51mm cylindrical protective black ceramic coated titanium shroud bolted to the inner casing
hardlex crystal
automatic Seiko 8L35, 26 jewels, 28.800/h) movement
600M pressure rating
polyurethane strap

Darth Tuna – All Black

SBBN011

Another five years later, in 2005, Seiko decided to technological change and update the Tuna slightly. A black DLC coated titanium inner casing was used instead of the gold-colored TiN. Furthermore, the gold DLC’d stainless steel bezel went black as well. And the gold-colored Philips screws, fixing the ceramic shroud to the inner casing, changed to black hex bolts. Finally, for the first time, a sapphire crystal was used instead of Seiko’s homegrown Hardlex.

The all-black appearance gave this watch its nickname ‘Darth Tuna’. And I guess, because of the all-black cylindrical appearance, this watch might have been the first one referred to as ‘Hockey Puck’ as well. The official Seiko reference for this watch is 7C46-0AA0 or model SBBN011. Here are the specs to compare:

SBBN011

reference 7C46-0AA0, model SBBN011, nickname Darth Tuna
large monocoque inner casing, made of DLC coated titanium, steel bezel black DLC’d
49mm cylindrical protective black ceramic coated titanium shroud bolted to the inner casing
flat sapphire crystal, ar-coated inside
high-quality quartz Seiko 7C46, 7 jewels movement
1000M pressure rating
polyurethane strap

A model we don’t know much about

S23611J1

It must have been after 2006, that a rather interesting, however not much known about, TiN coated ‘Golden Tuna’ surfaced. Its reference was 7C46-0AB0 and it had model indication S23611J1. It happens to be very much another re-issue of the 7C46-7008/SSBS018 re-issue presented in 1997. It’s said as well that this model was reserved for exclusive sales in Taiwan, however, this has yet to be confirmed. Specifications are known, they’re exactly the same as the last ‘Golden Tuna’ re-edition. The dial seems different, though and – mentioned in the case back – it sports a flat sapphire crystal.

S23611J1

reference 7C46-0AB0, model S23611J1, nickname Golden Tuna
large monocoque inner casing, made of TiN coated titanium, steel bezel gold-colored
49mm cylindrical protective black ceramic coated titanium shroud bolted to the inner casing
flat sapphire crystal, ar-coated inside
high-quality quartz Seiko 7C46, 7 jewels movement
1000M pressure rating
polyurethane strap

Speeding Up

SBBN013

It was 2009 that Seiko presented two new Tunas at once. After only 4 years the SBBN011 ‘Darth Tuna’ was replaced by the SBBN013, which technically was exactly the same watch. Even the reference number didn’t change, 7C46-0AA0, just as its nickname ‘Darth Tuna’. What did change was the dial and the crown. The dial of the SBBN013 was marked ‘Marine Master’, and the crown was signed with an ‘S’. This wasn’t the case with the SBBN011, for the rest, the watches are exactly the same. On the technical side, it kept the flat sapphire crystal as well as a ceramic shroud. No news here, however, I’ll list the specs to be complete:

SBBN013

reference 7C46-0AA0, model SBBN013, nickname Darth Tuna
large monocoque inner casing, made of DLC coated titanium, black steel bezel
49mm cylindrical protective black ceramic coated titanium shroud bolted to the inner casing.
flat sapphire crystal, ar-coated inside
high-quality quartz Seiko 7C46, 7 jewels movement.
1000M pressure rating
polyurethane strap

SBDX011

The second new Seiko Tuna introduced in 2009 was the 8L35-00C0, or model SBDX011. In fact, this was the 8L35-0030 Limited Edition Homage ‘Historical Tuna’ mainly aesthetically altered and brought out again. The blanc titanium casing of the ‘Historical Tuna’ received a black PVD coating, and it became nicked the ‘Emperor Tuna’. As a technical specification update, it received sapphire crystal instead of a hardlex. Just like the SBBD013, with its relatively equal all-black look, the 8L35-00C0 got ‘Marine Master’ printed on the dial. Author Michael Stockton did a nice comparative article on the ‘Emperor Tuna’ here. Please find its specifications below:

SBDX011

reference 8L35-00C0, model SBDX011, nickname Emperor Tuna
large monocoque inner casing, made of DLC coated titanium, black steel bezel
51mm cylindrical protective black ceramic coated titanium shroud bolted to the inner casing
flat sapphire crystal, ar-coated inside
automatic Seiko 8L35, 26 jewels, 28.800/h) movement
1000M pressure rating
polyurethane strap

Taiwan

Further to the rumors about the 2nd re-edition of the ‘Golden Tuna’ (7C46-0AB0) in 2006, it seems that in 2011 a black PVD coated reference 7C46-0AA0 ‘Darth Tuna’ (model S23619J1) was released specifically aimed at Taiwan as well. The reference for the watch (7C46-0AA0) was equal to the SBBN011 and SBBN013, technically the watch was much like it as well. The only difference could be the battery change date printing on the case back. As can be seen below, it had a signed crown like the SBBN013. While the SBBN013 had ‘Marine Master’ printed on the dial, the S23619J1 hasn’t, just like the SBBN011. I won’t mention specs here, as they are equal to the already mentioned ‘Darth Tunas’ before.

S23619J1

The 100th Anniversary of Seiko Watchmaking

Although the Seiko company was registered a few years longer, 2013 marked the 100th anniversary of Seiko Watchmaking. To celebrate this anniversary, amongst other special watches, Seiko introduced a Kinetic movement powered Tuna. Reference 5R65-0AJ0 or model SBDB008. With its golden accents and 600M depth rating, the watch had similarities with the first ‘Golden Tuna’. It, therefore, is often referred to as ‘Golden Spring Drive Tuna’.

However, I promised not to list Seiko Tuna models which don’t comply with the design rules and specifications of the original Seiko Tuna concept. And the ‘Golden Spring Drive Tuna’ doesn’t. Although its case is made of titanium, it’s is not of monocoque construction. It has a screw case back. Besides that, or probably even because of that, it has a domed sapphire crystal instead of a flat one. Ruining the resemblance to a tuna can.

SBDB008

The 5R65-0AJ0 ‘Golden Spring Drive Tuna’ was produced in a limited edition of only 300 pieces, mainly aimed at the Japanese market. One year later in, 2014, the same model, but in all black without gold accents, came as model SBDB009 available to the rest of the world. Presently it’s available as SBDB013.

Seiko Tuna Today

At the time of writing, early 2018, it’s already three years ago that Seiko brought us new Tuna models. In 2015, however, quite some modernized models were introduced. In the current international collection (which doesn’t mean all models should be available in your country) there are at least two variations of quartz driven models and two automatics. The SBBN025, SBBN027, SBDX01, and SBDX14.

Quartz-driven

SBBD025

To start with the quartz-driven models. The reference 7C46-0AH0, model SBBD025, is a second modern interpretation of the in 1989 introduced SBBN011 ‘Dart Tuna’. Same quartz movement, same case dimensions, same black PVD coating of the monocoque case, same size. I guess the nickname will become the same as well, however, it’s now sometimes seen as ‘New Darth Tuna’. What has changed quite a bit are the hands. Most eye-catching is the new arrow-shaped hour hand and the straight minute hand. These types of hands can be found on many other Seiko Marine Master and Prospex dive watches nowadays as well. It’s not the first time changes were made to the hands of Seiko Tuna watches, however, never was it that radical. At this time Seiko changed from polyurethane straps to soft silicone straps as well. A real advantage in my opinion. Here are the specs of the watch:

reference 7C46-0AA0, model SBBN025, nickname New Darth Tuna
large monocoque inner casing, made of DLC coated titanium, black steel bezel
49mm cylindrical protective black ceramic shroud bolted to the inner casing
flat sapphire crystal, ar-coated inside
high-quality quartz Seiko 7C46, 7 jewels movement
1000M pressure rating
silicone strap

SBBN02x

The Seiko Tuna SBBN027 model f.i. is technically exactly equal to SBBN025. The only difference is aesthetics. The color of the bezel inlay, dial, and the minute hand are yellow instead of black and white. All in all the appearance of the current quartz Seiko Tuna is quite different from the former models, technically, however, they’re not too far apart.

SBBN029, Limited Edition of only 700 pieces

The SBBN029 was a technically equal model as well, brought as a 700 pieces limited edition. Here are the general specifications for the current SBBN models:

reference 7C46-0A(x)0, model SBBN02x
large monocoque inner casing, made of DLC coated titanium, steel black bezel with different inlay colors
49mm cylindrical protective black ceramic shroud bolted to the inner casing
flat sapphire crystal, ar-coated inside
high-quality quartz Seiko 7C46, 7 jewels movement
1000M pressure rating
silicone strap

Automatics

SBDX013

The automatic Seiko Tuna, reference 8L35-00H0, model SBDX013 aesthetically changed even more compared to its ancestor, the ‘Emperor Tuna’. Except for the hands, the dial changed drastically as well. The date window no longer resides at 3 o’clock, it’s positioned between 4 and 5 now. A first in 40 years. For the rest here as well, the technical details didn’t change much. Same automatic 8L35 movement, same case dimensions, same black PVD coating of the monocoque case, same size.

reference 8L35-00H0, model SBDX013, nickname New Emperor Tuna
large monocoque inner casing, made of DLC coated titanium, black steel bezel
51mm cylindrical protective black ceramic shroud bolted to the inner casing
flat sapphire crystal, ar-coated inside
automatic Seiko 8L35, 26 jewels, 28.800/h) movement
1000M pressure rating of 1000M
silicone strap

SBDX014

The second model in the current Seiko Tuna automatic line up has the same reference, 8L35-00H0. Technically exactly equal to the latter, however here we find a totally new feature. Probably not mentioned at first sight, however, this is the first Seiko Tuna of which the bezel color is different from the (inner) casing of the watch. Just like the SBDX013, the SBDX014 has a black PVD coated titanium monocoque casing. However while at the 013 the bezel is black PVD coated as well, here with the SBDX014 the bezel has a rose gold color. Immediately resembling the former ‘Golden Tuna’, however being quite different in fact.

reference 8L35-00H0, model SBDX014, nickname New Golden Tuna
large monocoque inner casing, made of DLC coated titanium, steel bezel rose gold colored.
51mm cylindrical protective black ceramic shroud bolted to the inner casing
flat sapphire crystal, ar-coated inside
automatic Seiko 8L35, 26 jewels, 28.800/h) movement
1000M pressure rating
silicone strap

What We Missed And What Will Be Next

It’s here that I want to mention that I intentionally omitted quite a few Seiko Tuna models in this article. And then I’m not even pointing at the many wannabes Seiko Tuna models with non-monocoque casings and lesser pressure rating. However, there were monocoque, high pressure rated, models around which you didn’t find in this article. They were mostly special limited, or commemorative, editions aimed at specific global areas. You’ll find them named as White Dolphins, DIME MD edition, and much more. Technically they’re probably close to professional diver Seiko Tuna’s, however color-wise different. Thus for me too far off the original, and thus not the real deal where this article is aimed at.

As 2018 marks the 40th anniversary of the first ‘Golden Tuna’ – the reference 7549-7009 – I think it’s relatively safe to assume that Seiko will bring a homage to this historically important and iconic watch. The first ‘Golden Tuna’ in 1978 was Seiko’s first quartz powered professional diving watch. So I expect, and certainly hope, the homage will be equipped with the 7C46 quartz caliber. What I hope as well is that Seiko respects the original depth rating of the first ‘Golden Tuna’, 600M. We will see, I assume Seiko will introduce the new models during the Baselworld fair, which is only a month of waiting away…

Addendum

SBBN040

Meanwhile, as expected and mentioned above, Seiko presented the 40th anniversary ‘Golden Tuna’ model as a Limited Edition of 1978 pieces. A lot went well, it has the beloved and cheered 7C46 quartz caliber. It even has an old-type set of hands. The original encircled index markers are back, there’s no modern “Marine Master’ designation in the dial, nor a Prospex logo on the crown. We don’t care too much about the original Philips screws on the shroud being replaced with today’s hex-bolts. But what really bothers is the depth rating of the commemorative edition. That should have been 600M, just like the original ‘Golden Tuna’ of 1978. But unfortunately, Seiko chose for 1000M. Which for sure is the correct rating of this watch, however not adequate as the designation for the 40th-anniversary limited edition. Bluntly, now it’s a re-edition of the 1986 1000M rated SBDS018.

reference 7C46-0AL0, model SBBN040
large monocoque inner casing, made of DLC coated titanium, steel bezel gold colored
49mm cylindrical protective black ceramic shroud bolted to the inner casing
flat sapphire crystal, ar-coated inside
high-quality quartz Seiko 7C46, 7 jewels movement
1000M (Bummer!) pressure rating
silicone strap

Seiko Tuna References

The following models are mentioned in this article:

– reference 6159-7010, model YAQ028 (1975)
– reference 7549-7009, model PYF018 (1978)
– reference 7C46-7009, model SBDS018 (1985)
– reference 7C46-7008, model SSBS018 (1997)
– reference 8L35-0030, model SBDX005 (2000)
– reference 7C46-0AA0, model SBBN011 (2005)
– reference 7C46-0AB0, model S23611J1 (2006)
– reference 7C46-0AA0, model SBBN013 (2009)
– reference 8L35-00C0, model SBDX011 (2009)
– reference 7C46-0AA0, model S23619J1 (2011)
– reference 7C46-0AA0, model SBBD025 (2015)
– reference 7C46-0AA0, model SBBD027 (2015)
– reference 8L35-00H0, model SBDX013 (2015)
– reference 8L35-00H0, model SBDX014 (2015)
– reference 7C46-0AL0, model SBBN040 (2018)

We’ve made quite some pictures ourselves for this article, others were taken from several sources on the internet, like forums, Instagram and Pinterest. If anyone would like to be credited for one of the pictures used, being his or hers, please let us know and we’ll happy to mention you. We don’t have any commercial purpose in using the pictures, they’re just here for reference purposes.

For enhanced readability, this article has been updated in January 2020. Technical specifications on crystals and straps have been added, and the 40th anniversary model for the original ‘Golden Tuna’ as well.