Seiko Tuna – the Marinemaster Professional SBBN007

There are two categories of Seiko watch idiot savants: one considers that only a monocoque case (600m or 1000m) can be called a Tuna, the other considers that also a two piece shrouded case, the 300m Marinemaster Proffessional SBBN007, can be called a Tuna. I am in the latter category, even though I recently added to my collection a 1000m Darth Tuna, after reading this article. For me, any shrouded diver (however…with minimum 300m WR) as long as it resembles with a tuna can, fits in the Tuna category.

Back when I was just slightly scratching my watch addiction itch, every time I came across a picture or an article about a Seiko Tuna I was moving away as I found them…. well… here it goes: UGLY! They looked huge, un-proportioned, spartan, rough and potentially difficult to wear … and the list continued. 

As years went by I started to switch my focus more and more to Seiko divers. Inevitably, the Prospex Marinemasters could not have escaped my attention. Tunas represent an important category of the Marinemaster line up. The reason for this is that the world’s first professional diver issued by Seiko in 1975 was a … Tuna. But more on this later.

Years ago I had for the first time a quartz Seiko Tuna in my collection. To be honest, I was not fully knowledgeable of what actually a Tuna was back then. It was an SBBN017. From the multitude of relatively modern 300m versions released by Seiko in the last 15-20 years, I realized that this SBBN017 had the most attractive features. It has old style handsome hands, S marked crown, stainless steel bezel, no X on the dial, proud “Marinemaster” writing at 6 o’clock, nice bead blasted shroud.

As any respectable flipper I sold that Tuna. At that time I thought I would never look back in the Tuna direction. Little did I know … as here I am, couple of years later, owing two Tunas. A 1000m Darth Tuna and a 300m stainless steel one SBBN007. It looks like you can’t find a cure once the Tuna bug bites you. And I don’t even want to find one 🙂

In this review I will discuss about my SBBN007 300m tuna. This is the predecessor of the SBBN017 which I previously owned. This model came in two variants. 7C46-7010 produced between 1991 and 1996 and 7C46-7011 produced between 1997 and 2009. My SBBN007 is from August 2003. One cannot tell this is a 17 years old watch, without looking at the case back markings, as it looks quite fresh.

I’ll spend some time with a bit of history of the tunas in order to better understand the heritage and importance of this watch not only for Seiko but for diver watches in general.

Any Seikoholic knows about the letter that a Japanese diver sent to Seiko in 1968. He claimed that the crystals of his divers were getting cracked due to Helium building up pressure inside the watch. Seiko took this complaint seriously.

A gentleman called Ikuo Tokunaga, the one “responsible” for a number of famous Seiko divers designs and innovations, started to work on a 7 years long project together with a team of engineers. It resulted in 23 patents and the first Prospex diver in Seiko’s history: the first 600m Tuna 6159-7010 also called the Grandfather Tuna which had a hi-beat mechanical movement. In 1978 the Golden Tuna followed, which was the first quarz 600m Tuna 7549-7009.

I would like to mention that I was extremely surprised to see that Mr. Tokunaga takes time to respond to questions addressed by watch enthusiast (the responses are posted on watch forums) about his inventions in the 70’s which in my opinion changed significantly Seiko divers lineup. In one of his responses related to 1000m Tunas he mentions these words that went straight to my heart: “The watches are living machines and they wanted to be cared from their lovely owner with heart-full mind every day. Please love your professional 1000m diver watch for ever”

In 1978 Seiko also released the 7549-7010 quartz 300m Professional Diver’s. It had a standard two-piece case and an extra screw on retention ring to secure the crystal and prevent helium gas penetration. The main case and protective cover were made of stainless steel. It was the first 300m Tuna.

In 1986 Seiko released the first 1000m Tuna, also with a quartz movement. The notorious 7C46 which…. 35 years later is still in production and is the heart of the modern Tunas. You can find this movement ONLY in Tunas.

Now before I turn this review into a history lesson let’s go back to my 300m Tuna 🙂

At a first glance the watch looks intimidating due to the mean looking profile. The size on paper is not less intimidating either. At 47.2mm diameter with a thickness of 15mm, this fits the profile of a big watch. However, an important dimension which contributes a lot on the wearability is the lug to lug, which is … 44.5mm… I dare you find another watch (besides Tunas) that has a lug to lug smaller than its diameter :).

And please bear in mind that the 300m still have some sort of lugs … while the monocoque Tunas don’t have any kind of lugs. Therefore, the lug to lug is even smaller than the 300m Tunas even if the diameter is bigger.

Having a quartz movement, the weight is not that big, at 92g (watch head only). The 22mm lug width makes this a versatile watch in terms of being able to use your leather, natos and rubber straps one may have.

The dial of this SBBN007 makes it stand out from the other 300m Tunas as the lume markers have crop circles which creates a pleasant appearance (not looking cluttered) making the dial look even smaller (SS bezel contributing to that too). One important aspect is that the word “Marinemaster” is missing from 6 o’clock, with only “Professional 300m” written on the dial. This may be a downside for some, but I don’t mind that. Actually, I think that only the word “Seiko” at 12 o’clock creates a nice balance.

The hands are a thing of beauty! Polished flat metallic look with generous lume applied, with the hour and minutes hands perfectly differentiable one from another however keeping the same design cues. The seconds hand has the short part with the lume lollypop in black color while the long part is white. This makes it look very cool as most of the times you see only the white top part and the lollypop moving.

The day and date window is nicely framed with the same white line, like the hour markers crops. The day has English and Kanji language (as any JDM watch) with SAT blue and SUN red (as any other Seiko). This a feature that I enjoy a lot!

The shroud has a nice bead blasted finish with a matte gun metal grey look. It is fixed with 3 Ponzi head screws, unlike 1000m Tunas that have 4 screws. The shrouds on the Tunas are usually getting marks and scars which imo contributes to the watch character. I sometimes remove the shroud and clean its interior, then operate the bezel under warm running water in order to remove any debris.

The crown is not signed and is easy to grip, even though I rarely operate it. The lugs are drilled and are extremely short. However, there is a nice practical thing which I have never seen before on any another watch. Only one side of the lugs is drilled. This makes perfect sense as when the spring bars are removed is enough to stick your tool only into one side :).

The Lume is still strong after 13 years. It glows like a torch when I charge it with my Iphone flash light before I want to post a picture on a WIS WhatsApp group or a watch forum (greetings to my WristSushi forum fellows) :). I can still read the time at 4-5 in the morning, which makes this a perfectly functional watch from this perspective.

The crystal is a doomed hardlex. In my opinion, it is a perfect match for this watch case and dial and creates the perfect diver look. The previous Tuna I had was fitted, with a doomed sapphire green AR coated crystal. This is a nice touch if you are afraid that hardlex may scratch. I did happen to scratch my hardlex crystals.

The movement….well…people have written a lot on forums and dedicated articles. This is a magnificent movement. I think the simple fact that Seiko decided to use it in the last 35 years exclusively for the Tunas, means a lot.

The battery life is more than 5 years and the End Of Life indicator makes the second hand tick two seconds at a time, letting you know is time for a battery change. I believe I read somewhere that this happens for couple of weeks before is completely dead. It’s accuracy makes any of my non atomic Gshocks blush. I am getting less than 5-10s per month deviation depending on how much I wear the watch in that month. It has 7 jewels, high torque (allowing the use of the big heavy legible hands) and dual-rate trimmers. These allow the watch to synchronize perfectly, offering high accuracy. These are fully serviceable movements as any other mechanical one. I am sure it will last for many decades to come.

As a conclusion, I think any WIS should not be fooled if at the first glance a Seiko Tuna may look ugly to him/her and give one a try. There are many options out there with 300, 600, 1000m WR; all range of movements: quartz, hi beat or spring drive; various color/material options with Stainless Steel, Titanium, Ceramic; bracelet and rubber straps options. These are proper tool watches, reliable in any conditions. They have a unique look that is instantly recognizable and cannot be mistaken with any other watch out there.

Enjoy your watches and keep practicing social distancing!

Stay safe!

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