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In the 1970’s Seiko changed the watch world forever. It’s open to debate whether or not that change was a positive or a negative one, but it was changed nonetheless. It was in 1970 that Seiko unveiled the Astron, the world’s first Quartz electronic watch at Basel World. Switzerland drew back in fear. What followed was known as the “quartz crisis,” and many strictly mechanical brands didn’t survive the coming years. This is, in my opinion, Seiko’s most notable achievement in the Horological landscape. It is not, however, the only thing that sets them apart from other watch manufacturers.
For many years Seiko has made mechanical watches that were comparable to their peers in Europe. Some of these pieces have long lines of heritage and aggressively devoted fans. The vintage Seiko collector market is alive and well online.
Seiko makes a lot of strictly “tool watch” divers, like the new Turtle Reissue, the Sumo, the SKX173/SKX007, and the Tuna lines. All of these watches fall under the banner of Seiko’s Prospex, literally meaning “Pro-Specs”, or watches that can and will perform under heavy and serious use.
At the top of the heap on the Prospex line is the Seiko Marinemaster 300, or the SBDX017. The MM300 fits a weird place in a watch collector’s collection. Seiko, is typically viewed as a “budget,” brand (in spite of their super high end offerings). The MM300 sits right between entry level high end watches like some Orises and Hamiltons and true Swiss luxury watches (ex. Omegas, IWCs, Rolexes.) Let’s look a little at what goes into something like that, but first some specs:
Lug to Lug: 48.4mm
Case Thickness: 15.45mm
Lug Width: 20mm
Weight w/Bracelet: 7.1oz (201 grams)
The Marinemaster, excluding everything else, is a big watch. It wears big and looks big. Big isn’t always bad, however. On the bracelet the MM sits low and well on the wrist. When you read other reviews about this watch this is a matter of some contention. This watch wears differently on different people. On my wrist the bracelet sits well, so the watch wears well. However, if your wrist is too narrow or to large it can make the bracelet fit poorly.
On me it’s comfortable and largely unobtrusive. The crown at 4 o’clock goes a long way to make this piece easier to wear for long periods of time. At work I spend a decent amount of time standing at counters or waist height tables, and I rest my hands palm down on them while talking to people. Normally, with a watch that has a 3 o’clock crown, it can start to press into the back of my hand and feel uncomfortable. The recessed 4 o’clock crown helps with this issue.
The MM300 uses a 8L35 Automatic movement. This is an undecorated/unregulated version of the Grand Seiko 9S55 movement. It’s the pinnacle of a sports watch mechanical movement, at least that Seiko uses. It’s built for reliability and robustness. My personal example is keeping +3.4s/day. Now a certified chronometer specs require a watch to keep an average daily rate of -4/+6 seconds per day. So… my SBDX017 is keeping “Contrôle Officiel Suisse des Chronomètres” (COSC) Standard. In order for a watch to be officially certified as a chronometer the movement has to be sent to the observatory in Switzerland. Obviously, Seiko does not do that and that translates into a more affordable watch for you.
All of this being said, the 8L35 movement is unregulated. This means that after the movement was manufactured it was then cased, vs. adjusted manually before being put in a watch case. Long story short, MM300’s can have a spectrum of accuracies and it really depends on which example you get. Mine is excellent, but if you read online you’ll read stories of +15/-10s a day, which is what this movement is advertised to keep. Just something to keep in mind.
The case of the Marinemaster 300 is really where it begins to take on some character of it’s own. This watch is cased in a Monoblock case. This means the entire contents of the watch are loaded via the front and sealed by the crystal. There’s no removable case back. That is something that is fairly unusual when it comes to watchmaking these days. Most watches have removable case backs. The intention behind Seiko’s design here is to remove one point of ingress for water.
Apart from the Monoblock case you are treated to Seiko’s excellent finishing; beautiful bevels and transitions, crisp lines and delicate touches. The steel case is coated with Seiko’s “Diashield,” coating. Diashield is essentially a scratch/wear resistant coating that goes a long way to repel normal wear marks that your watch might acquire throughout the day. I have found Diashield to be extremely effective, and frankly, a godsend in keeping a “tool” watch looking good. If you bang your watch hard enough you will still get a scratch or a ding, but Diashield will prevent the normal day-to-day knicks pretty well. The MM300’s case is one of the highlights of this watch. It oozes quality and reliability–exactly what you’d expect from a high end diver like this.
The Marinemaster’s crown is a simple signed crown placed at 4 o’clock. The winding action is smooooooth. I find it’s smoother than some of my Swiss pieces. It is a screwdown crown, as you’d expect from a diver’s watch. The most notable trait of the SBDX017’s crown is the placement. At 4 o’clock, as I mentioned earlier, it won’t dig into the back of your hand over time.
Dial, Crystal, & Bezel
The Marinemaster’s dial is a case study in legibility. The hour indices are applied and lumed. The 6 and 9 o’clock have rectangular markers, whereas the intermediate hours are round. The noon, is an angled double rectangle. All of these markers have large “dollops” of lume set in them and the same is true for the hands. Seiko’s lume is that of legends, glowing brightly even in broad daylight. This is one area I can promise you, that will not let you down about this watch. The borders of the hands and indices are polished steel which offers a nice dimension when you’re looking at the dial at an angle. The dial itself is matte black, with painted white text. It’s a wordy dial, but I guess that depends on your perspective. Personally, I think that the text lends itself to the MM300’s “tooly” appeal, whereas other’s would prefer a simple aesthetic. So that’s up to you.
The SBDX017 takes a lot of flack for their choice to continue using a hardlex crystal on a watch that sells for over $1500. I’ve had mixed experiences with it myself. I managed to scratch the Hardlex on my Seiko Sumo, but I suspect that was more my fault than the materials. That being said, there are sapphire aftermarket options available. I like how the hardlex looks in the light, and since the “Sumo incident” I haven’t had any marks or issues on the crystal of any of my other Seikos.
Bezels, ahh bezels… After all what is a good dive watch, without a good dive bezel? The Seiko’s is perfect. Large, extremely legible, and easily used. What you want from a diving bezel, in daily use, is something that is easily (not too easily) turned and set so that you can see elapsed time. When I am wearing a diving watch, I use the bezel for everything from keeping track of breaks to timing coffee french presses. The SBDX017 does this well.
One thing Seiko does not do very well, in my opinion, are bracelets. You can get OEM bracelets for most Seiko divers. This includes everything from the SKX line to the SRP line and above. The lower end bracelets feel and are cheap. With that said, the SBDX017 bracelet is polarizing. IF it fits you, it fits you really well. The catch however is that the links of the SBDX bracelet are long and don’t articulate in the middle like some brands do. What this essentially means is that depending on how the watch drapes on your wrist the links may stick out abruptly. It fits my wrist very well, and that really makes or breaks this watch. Alternatively, a friend of mine has the exact same MM300 and a link juts out where the bracelet drapes over a wrist bone. So, it really depends on how the watch fits your specific case.
The clasp on this bracelet is interesting with it’s ratcheting diving extension. You activate this by pulling up on the fold over piece and then it slides out. This can happen often by accident, and I almost always do it when I am putting the watch on. The benefit to a clasp like this is if your wrist swells a bit during a warm day you can pop it out one click to keep it comfortable. Seiko’s solution is purely functional and does not look good when expanded. There are other brands like Rolex or Omega that do this much better and maintain the aesthetic of their bracelet while expanded.
Seiko Marinemaster 300 SBDX017 – Final Thoughts
A few months ago I was leeching wifi off of a hotel bar on the island of Bequia. Bequia is the second largest island in the Grenadines, a reasonably quiet place, but still one that focuses on tourism. Along the waterfront walk of Port Elizabeth there are a few dive shops that have been there forever. While I was waiting for my photos to upload and my next umbrellaed beverage to arrive, I noticed an older guy unloading air tanks from a dive boat and hauling them into one of the nearby dive shops. On his wrist was an old Seiko dive watch.
This is the legend isn’t it? In my mind I started telling a story of this dude arriving on the island when he was younger with a knapsack, regulator, and a dive watch; and he lived the island life. In my story, he settled into island life, opened a dive shop, and had adventures. That’s the dream isn’t it? Buying a tool watch, and then just…doing life with it, using it as intended.
The SBDX017 is the perfect piece for that. It’s robust, it’s durable, and it can take you anywhere. It also takes a big wrist to wear. Some people might have a little heartburn spending the money on a Seiko, but they are truly great. There are other diver’s from Seiko that you could go with, a Turtle or perhaps a Sumo, but the MM300 is top of the heap.
- Automatic Movement with 50-hour power reserve
- Dual Curved Hardlex with inside anti-reflective coating
- Japanese-automatic Movement
- Case Diameter: 44.3mm
- Diver’s 300m (984ft) watch: in general, suitable for mixed-gas diving
I recommend purchasing the Seiko Marinemaster 300 SBDX017 at Amazon. Please consider that purchasing anything through any of the links on this website helps support BladeReviews.com, and keeps the site going. As always, any and all support is greatly appreciated. Thank you very much.
Bob B says
A thoroughly well written and enjoyable article. The MM300 is definitely on my wish list. Along with retiring in the Grenadines. 🙂
Thanks for checking out the review and taking the time to comment! I agree the MM300 is a covetable watch!
I Love my MM300 and will never part with it.
It will be left to my son along with my 6105 8110 & the Bullhead chrono.
A really good and well thought out review (thanks) and I love both of my MM300s 🙂