December 26, 2006

The Seiko Marinemaster page

SBDX001, link goes to source pageSBDX001, link goes to source page

What this page is

I’m debating a watch, the Seiko Marinemaster SBDX001. This page is a collection of my notes and finds as I did the product research and reading. It’s posted here (and will go to SCWF as well) as a service to other people considering it.

I don’t own one, so all of the pictures here are copied from other sites. Whenever I’ve done so, the picture is a link to the source site to provide attribution.

I’m experimenting with formatting, for now I’ll put the source links at the end of the page.


There’s more than one model of Seiko called Marinemaster’, so to distinguish this one I’ll call it the MM300 to distinguish it from the 600M spring drive version. Both are part of the Prospex’ line of watches, Seiko’s upscale diver line that’s only sold and marketed in Japan. (There are other Marinemasters as well, this page does not cover them.)

The MM300 designed for saturation diving, up to 300 meters, and is equipped with a special L-shaped gasket and one-piece case to render it proof against helium gas. Unlike the Rolex Seadweller and Omega Seamaster, a helium escape valve is not needed due to the superior seal - a more elegant solution, in my opinion.

It’s a large, heavy watch - 14.6mm high by 44mm across, 209g on the included bracelet, 136g on the rubber strap.

The watch comes with a rubber strap as well.

The official product page, in Japanese, is here.


Back of watchBack of watch

The case is made of stainless steel, I assume type 316L but I’m not sure. It’s monocoque, meaning that the back does not come off and the movement is accessed after removing the bezel and crystal. Seiya claims it’s antimagnetic as well; I’ve not seen anyone else mention this. Drilled lugs, unsigned screw-down crown.


The movement is an 8L35, an undecorated and unadjusted version of the high-end Grand Seiko 9S55. Rhodium-plated, 26 jewels, automatic, 28800vph (4Hz), handwind and hacking, 50 hour power reserve. The size of the balance wheel was increased to provide the torque required, as the hands are heavier than a dress watch. The 8L35 is also used in the Landmaster, which has the same hands.The movement by all accounts keeps excellent time, and in 9S55 trim is capable of exceeding COSC specs. Anecdotal reports on various fora indicate less than five seconds’ daily error is typical. The spec is -10 to +15 seconds per day.The 8L35 is completely in-house Seiko, and is descended from the 6159 300m diver, circa 1969. Everything from oil on up, including mainspring, is Seiko. Kinda cool. What they call a manufacture’. John ei8htohms’ Davis is a big fan of the 8L35, and had this to say about it:

My understanding is that the Seiko 8L35 is pretty much the same movement as the 9S55, but perhaps missing a few refinements and not as thoroughly adjusted. As such, it is one of the finest automatic movements Seiko makes. The machining is of the highest quality and the design and construction is informed by Seiko’s many years of experience. I believe the 8L35 even has a Lossier inner coil on the hairspring. A very nice touch you will not find in any modern Swiss watches to my knowledge.

In a different thread he elaborates on Lossier inner curves, pinned hairsprings and fine adjustments, well worth a read if you want to know more. I liked this quote:

As far as the movement is concerned, it is a wonderful piece of work that is exactly what it claims to be: a grand Seiko movement. The finishing is almost entirely machined, but machining of exquisite quality overall. The edges are generally not chamferred (anglaged), but are incredibly crisp and the sides are cut to a near mirror polish (as can be seen in some of SteveG’s pics).

Since the case is one-piece, there are very few pictures of the movement around. Here’s the official one from the product page:

Update 8/29/07: A new thread on Timezone has 3 large pictures of the movement.

Update 3/20/08: The movement is hand-assembled in northern Japan by a staff of 21, see this post for details.

Strap and bracelet

The included bracelet is 20mm, tapering to about 18mm at the clasp. Solid links, flat Oyster-style with slightly raised center link. Center links are partially polished. It’s held together with the Seiko pin-and-collar system. Solid end links, fliplock with push release and ratcheting wetsuit extension. Each link is actually five discrete pieces. As noted above, the lugs are drilled which makes changes easier.

The included rubber strap is a variation on the Z22 that Seiko uses on its SKX-series divers. (Note that its 20mm, not 22, so it’s really a variation of the less-common Z20.)

Here you can see the wetsuit extension in use, works well by most reports. Nice for warm days as well. If you look at this and the above picture, you can see that they changed the extension slide a bit, so which type you get depends on the age of your watch.

Crystal, bezel and face

The hands are interesting, a superbly detailed combination of brushed and polished finish with Lumibrite infill:

Very legible, though they could be a bit longer. I’ve noticed that Seiko and Citizen seem to use shorter hands than European brands. Aesthetics, I assume.The text on the face is a bit verbose, which is a negative for me. Unlike the newer SD600, the crystal is domed Hardlex, with an exterior anti-reflective coating. It sits just below the sloped bezel, and is therefore less likely to be damaged. According to Ikuo Tokunaga it’s mainly a question of economics and resistance to impact. Jack at Industrial Watch Works will replace it with sapphire for about 200USD. Bezel is 120-click and sloped. From Alphonse on SCWF, an interesting tidbit about it’s construction:

The MM text is printed directly onto the bezel in a multi step process. The metal bezel’s top surface is blackened and then the printing lasered onto the black paint”. So in other words, the bezel is a one piece assembly.

I found this out the hard way when I needed to have one replaced from a very nasty series of gouges caused by a knurled barbell. The entire bezel had to be replaced by Seiko since there is no traditional insert”.

The same thread also discusses the fact that you can scratch the bezel pretty easily, which makes sense if its 316L steel.


Seiko is well-known for excellent luminosity, and the MM300 is no exception. Lumibrite, their version of Super Luminova, is applied liberally to hands, indices and timing dot:

The bezel indices are not lumed.

Price and availability

The list price is 262,500JPY, or about 2,200USD as of 12/2006. Since it’s Japan-only, you have to either book a flight or find a dealer who will ship it. You also want to ensure the dealer is authorized and will handle warranty service, if required.

  1. Higuchi has an excellent reputation and, as of today, the lowest quoted price at 185,000JPY. (~1,600USD)

  2. Seiya also has them, also is well-respected, but as of today is a bit more expensive.

  3. If you speak Japanese, WatchTanaka site has them as well.

You can find them used on the TimeZone sales corner, the Seiko-Citizen trading forum, or the Poor Man’s watch trading and sales forum. Expect to pay 1200 to 1400USD for a used one in good condition as of 12/2006. This seems to indicate strong demand and good value retention.

Negatives and drawbacks

There’s significant controvery around the MM300. For many Seiko fans, it’s considered a grail watch’, yet there’s some unhappiness as well. The Hardlex (instead of the sapphire expected at this price point) and Japan-only service are commonly cited. The unsigned crown also nets complaints. The only domestic repair is Jack at IWW, and that’s not covered by warranty.

There have been reports of the crown threads being damaged, such as this thread. However, Bongo on SCWF did a complete search of the archives and finds no factual basis for it.

Overall, the negative comments are greatly outnumbered by the positive ones, so consider accordingly.

More information and sources

I mainly used Google, TimeZone and the SCWF while researching this. And SteveG’s pictures, of course.

Other reviews (and discussion) of the watch

Here is a thread discussing service issues, Seiko Japan versus Industrial Watch Works(IWW).

Comparisons to other watches



Amazingly, a video of the MM300 is here on YouTube.

History, other Seiko divers

This page (Titans of the Deep) has a detailed history of Seiko divers, quite interesting. Mostly about the shrouded divers’, some of which also use the 8L35 movement.

The Legacy of Seikosha has lots of details about the company and brief sketches of the various movements.

Update 1/1/07:

Reviews Watches Seiko

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