- Date acquired: Apr 21 2007
- Production date: Mar 2007
Source: Higuchi Inc, Japan
- Price paid: JPY47,000 (USD429)
- Status: In production
When stock photos of the SBDC-series divers first appeared on the Internet in early 2007, it created huge ripples in the watch forum communities. It caused widespread excitement and speculation among the Seiko diver watch fans. This was the watch that Seiko enthusiasts had been eagerly anticipating for a very long time. It wasn’t just the fact that these were entirely new models, they were also the first Seiko divers based on the relatively new manual winding and hacking 6R15 automatic caliber.
The 6R15 movement itself is a superb architecture, somewhat based on the entry level 7s caliber and striking a perfect balance between production cost and complexity. The 6R15 debuted with the SCVS-series Seiko Spirit dress watches sometime in 2005 and had enjoyed modest popularity worldwide.
Seiko designed the SBDC series to fill the void left by the technically slightly more superior 4s15 based divers. It’s a well crafted mid-priced automatic diver, nicely fitting between their high end SBDX001 Marine Master and their cheaper 7s25 SBDA-series mechanicals.
Prior to the introduction of the SBDC divers, Seiko left a void with the discontinuation of the highly regarded SCVF001/003 models powered by the 4s15 caliber. The twenty five jeweled 4s15 had everything the 6R15 offered plus a desirable high beat movement (28,800 bph). The hackset feature is nothing really new to Seiko diver family, as certain vintage movements such as the 6105B and the very rare 6306 both offered second hand stopping for precise synchronization with the time signal.
Above: A discontinued SCVF001 diver with the high beat 4s15 caliber
Finally, Seiko offered a modestly priced mechanical diver with auxiliary hand winding and a hacking ability (to stop the second hand for time synchronization) that many Seiko enthusiasts desired. Until the advent of the SBDC range, mechanical Seiko diver collectors had to be content with the ubiquitous 7s-caliber which is in fact, Seiko’s entry level movement.
It’s either the 7s caliber or going up all the way to the flagship, hand assembled SBDX001 Marine Master with the top notch 8L35 movement. Seiko just had nothing to offer in between.
The forum threads quickly expanded with many enthusiastic and skeptical posters airing their personal views. Some thought it was a great looking diver. Others dismissed the SBDC’s unbalanced aesthetics – an oversized watch with a rather skinny bracelet. I began to follow discussions on the new SBDC series with great interest. There were no real world pictures to make more accurate assessments as there were only the stock pictures to look at.
Seiko’s catalog photos are usually flat-looking, devoid of depth and their watches actually look better in real life. Below are the first official pictures of the Sumo divers when they first came out. Unfortunately, they didn’t really tell much about the watches. How big were they? Were the lug sizes 20 or 22mm?
Three guises of the SBDC divers were simultaneously released – two models with stainless steel bracelets (black SBDC001 and blue SBDC003) and one orange dialed SBDC005 on standard 20mm polyurethane rubber strap.
As with Seiko’s marketing tradition, their orange dialed dive watches are usually fitted with rubber straps from the factory. Why is this so? Some folks theorize that Seiko feels that their customers who choose an orange dialed diver’s watch are likely to actually wear them for diving activities. Therefore it probably made sense to have them factory fitted with rubber straps.
However, Japan based vendors like Seiya Japan and Higuchi Inc are able to include the stainless steel bracelet upon request for a small additional premium.
Stock photos from Seiko. (from L-R: SBDC001, SBDC003, SBDC005)
While waiting for the SBDC series to released in Japan, watch pundits played a game of nicknaming the new 6R15 diver. There were several suggestions, ranging from the comical and vulgar-sounding “camel toe” (due to the appearance of the V-shaped 12 o’clock marker) to a rather austere sounding “Scuba”. Others preferred to call it the “Shogun”.
Factually, Seiko brands their professional range of divers as “Professional” and “Scuba” for their recreational line of divers. Therefore the “Scuba” moniker didn’t really create an impact with the eagerly waiting buyers as there are other Seiko Prospex divers that are officially named “Scuba”.
In the end, it was generally accepted that the SBDC line of divers were to be known as the “Sumo”. Many thought it was a befitting nickname as the new 6R15 divers were larger large and fat like a real Sumo wrestler. Although I’m not particularly fond of the nickname, for all intents and purposes I will use the popular moniker “Sumo” alternately when referring to the SBDC001 in this review.
Look and feel
I finally decided to pull the trigger on the black SBDC001 to be on the safe side. The catalog photo of the blue SBDC003 didn’t show its true color – the dial looked somewhat a deep blue. As I already own the blue SBDA003 Titanium Samurai, I thought black was the best color. Mind you, this is not exactly a cheap watch so I had to make a careful choice.
The SBDX001 Marine Master was too rich for my blood so the black SBDC001 was the perfect pick. I naturally ordered one from Higuchi, a renowned watch seller based in Japan who caters for overseas orders. The other source was Seiya Japan, but I chose Higuchi as I had bought from him twice in the past.
I was astounded to see how large the Sumo was when I drew it out of its yellow Prospex cardboard box. It was even larger than my SBBN007 Tuna! I was pleased with the fit and finish the watch – for a mid-priced Seiko diver it was certainly a very well made timepiece.
My SBDC001 diver when I opened the box for the first time
Bezel, crystal and case
The SBDC001 is adorned with a slightly domed mineral crystal (Hardlex). It’s almost flat and is fitted flush with the bezel. The bezel itself is top notch – not only it is constructed out of a solid chunk of stainless steel, it also turns smoothly with precise 120 graduated clicks. A unique design element is the semi-shrouded case, which protects the left and right sides of the bezel.
The Sumo’s case is a blend of finely polished and matte surfaces. It seems much attention was given to the polishing process. I really like the pronounced sculpted edges of the case – it reminded me of the more expensive SBDX001 Marine Master minus the high asking price.
The crown has an embossed “S” (for Seiko) sign, which is a very welcome feature. It unscrews and screws in quite effortlessly. To manually hand wind the movement, you have to unscrew the crown to the first position and rotate it clockwise. There should be a slight gritty feel as you wind the mainspring – if it’s too smooth then the crown may not be engaging the winding mechanism.
Side profile views of the SBDC001 and close up of the signed crown (borrowed photos)
Early faulty Sumo divers
That said, there had been documented cases of faulty hand-winding Sumos. The first SBDC001 that was delivered to me was unfortunately one of them. It would sometimes wind the main spring and then it refused to wind at all. There was no feedback when I hand wound the watch. The crown was obviously defective.
The culprit was not the main spring as the oscillating rotor could wind the watch automatically. So it had to be the crown that wasn’t engaging the winding mechanism. I sent the watch back to Japan at my cost and Higuchi replaced it with a properly hand winding one.
I also noted that some Sumo divers unfortunately have chapter rings that don’t line up perfectly with the index markers. For a USD400-plus (now the price has crossed the USD500 barrier) watch I would have expected better quality control from Seiko. This is however, an aesthetic defect rather than a mechanical problem.
Many people have fielded this question: “Is it normal for the crown to feel gritty when I hand-wind the Sumo?" The short answer to that is yes. Most, if not all hand-winding automatics should have that gritty, ratchety feel when you turn the crown to wind the main spring. If the crown turns too smoothly when you wind it, something’s definitely not right.
A photo of the 6R15B movement used in the SBDC-series divers (borrowed pic)
Another popular query is if the watch is supposed to wind as you’re screwing-in the crown to lock it. Again, the answer is also a resounding yes. There seems to be a lack of a clutch mechanism to disengage the manual winding when you screw in the crown into the case.
If your crown doesn’t feel gritty while you’re locking it then the watch you may have a crown problem.
My theory is that the SBDC-series divers were Seiko’s first watches with screw-in crowns based on the 6R15 caliber and the engineers probably didn’t get the crown design right.
I’m not sure if it’s a design or a quality control issue but one thing’s for certain – it is certainly not typical for Seiko, renowned for its robust and reliable movements to have faulty winding watches.
The hand-winding issue is not due to the 6R15 movement itself because the caliber has been used in the Seiko Spirit dress watches long before the Sumo divers were introduced. The 6R15 movement is quite reliable. Unfortunately the crown is not, but I’m sure this issue has been fixed by Seiko since then. By contrast, I have yet to hear of complaints of 6R15 based Seiko Spirits and Alpinists having hand-winding problems.
The misaligned date issue
Now we move on to the most common complaint: the slightly misaligned date issue. It turns out that this is a random trait affecting some, but not all Sumo divers. While I don’t think this is a technically a manufacturing defect, it’s an aesthetic flaw that plagues discerning Sumo diver owners.
My first SBDC001 was aesthetically perfect, the chapter ring and date alignment were fine, save for the non-winding crown problem. The replacement watch was the total opposite! Go figure!
The date so happens to sit a bit too high and not squarely centered on the date window frame. The upper part of the date digits almost touches the top inner calendar frame but falls short of disappearing into the frame.
Fortunately, this can be fixed by a competent watchmaker or at the Seiko service center. If your Sumo diver suffers from this minor flaw, check with your country’s authorized Seiko repair center if they can fix it under warranty. As the SBDC divers are for the local Japan market, its warranty is valid only in Japan.
There’s a possibility that your Seiko repair center may refuse to undertake this minor job for free, therefore check with the service center personnel first. Another issue is whether the Seiko’s service center’s technicians are familiar with the 6R15B movement, which is not a commonly found caliber outside of Japan.
The Seiko repair center staff would usually inspect the watch first. If the frontline staff feels that they can’t handle the 6R15B or the Sumo diver, don’t pressure them into attempting the repair. The last thing you want is some inexperienced technician accidentally scratching your prized Sumo diver in an attempt to disassemble it or even worse, messing up a movement he is not familiar with.
If this is the case, it would be safer for your watch to be shipped to Seiko Japan for the date realignment job.
The Sumo is a fairly large watch and I think you should consider the measurements before you buy one. I like big timepieces (but not ridiculously big) and I have no qualms with the Sumo. Here are the dimensions for your perusal:
- Diameter: 45 mm (w/o crown), 48.5 mm (w/ crown)
- Lug-to-lug: 51 mm
- Thickness: 14 mm
- Lug width: 20 mm
- Bracelet width: 19 mm, tapering to 18 mm at clasp
For a better perspective, have a look at the photos below for size comparisons with some of my other Seiko divers.
That’s right folks, it’s a large watch but not ridiculously large like some Casio Pro Trek multi-sensor watches or Nautica fashion timepieces. Personally, I can tolerate wearing my Sumo diver compared to my former Casio PRG40T-VDR Triple Sensor, which tips the scales at over 52mm in diameter!
Please note that I shot the comparison photos in macro close up mode at the camera’s widest focal length. Objects nearest to the the lens tend to be exaggerated in size, therefore the Sumo diver appears to be overwhelmingly gigantic compared to the other watches.
Comparison photos of the SBDC001 with other popular Seiko divers. Click on the individual photos for a bigger view.
The Sumo comes with a 20mm stainless steel bracelet. It’s a standard fare from Seiko, with a diver’s extension clasp. Nothing to shout about, really. Thanks to the non-integrated lug design, some owners have replaced their bracelets with classy aftermarket leather straps.
For some reason, Seiko favors 20mm lugs for most of its Prospex dive watches. The SBDA-series Ti Samurais have 22mm lugs which made the Samurai more aesthetically balanced. For its huge diameter, the Sumo’s paltry 20mm lugs somewhat makes the watch look even bigger. Many owners felt that the SBDC divers should have wider lugs to match the sheer girth of the case, myself included. It’s not just cosmetics – the heavy Sumo diver ought to have 22mm lugs so that a wider strap can be fitted if so desired.
The lugs leave a lot to be desired. I noticed that the end pieces (where the bracelet meets the watch case) are somewhat recessed instead of being flush with the plane of the lugs. I’m not sure if the designers did this intentionally or the bracelet end pieces weren’t mounted properly.
On the wrist however, the Sumo is a wrist hugger and seats rather nicely. It doesn’t flop around nor slide down your wrist provided that you don’t wear it too loosely.
Dial and hands
The Sumo has a very striking looking dial, true to Seiko’s tradition of high contrast dial artwork. It is an interesting blend of new and old – the hands resemble the SBDA-series titanium Samurai divers while having its own identity. The hour hand has a single chevron-like frame in the middle while the minute hand resembles the SBDB001 Prospex 600m Spring Drive diver’s minute hand. The second hand, with a “stop light” lumed tip appears to be borrowed from the SBDA-series divers.
There’s a quirk with the date display – the date is unfortunately aligned a bit too high in the window and not perfectly centered as it should be. This seems to be a common trait with Sumo divers and many owners of this watch echoed the same complaint. I hope Seiko will rectify this fault in their future batches.
An oddity is the use of italicized font for the “Automatic” text. This is the first time Seiko’s used italics in a diver’s watch. It somewhat softens the tough looking facade of the watch and gives it a slightly dressier look.
Above: A borrowed photo of the Sumo’s lower dial. Note the scripted “Automatic” text.
The SBDC001 is undoubtedly one of the lume champs from the Seiko stable. I was elated to find out that Seiko chose the yellowish-white lume, which possesses extra sensitivity to ambient light in addition to its supreme brightness. It’s the same kind of lume used in the Sawtooth, Knight, Monster and SBDQ/SBCB Prospex divers, beating even the Prospex SBDX001 and SBBN007 divers.
You don’t need to expose the Sumo to very bright light sources – even a typical office’s overhead fluorescent lighting is enough to charge the lume. The lume starts off very bright and gradually dims as the hours go by. The dial markers and hands are still visible after seven hours in darkness, provided that you have sufficiently charged the lume beforehand.
Its fierce luminosity should satisfy the most demanding lume junkies!
Sumo Diver Mods
The Sumo diver. unlike the extremely popular SKX007K diver is considered an expensive watch by many Seiko owners’ standards and many prefer to keep them as stock as possible. To date, I have not seen any radical customizations made to the SBDC divers apart from subtle upgrades to sapphire crystals or a simple white-on-black date calendar swap.
Above: A nicely done SBDC001 mod with an aftermarket sapphire crystal and a black date disc. Pictures courtesy of my good friend and fellow Seiko collector, “Ptolemy". Modification performed by Duarte Mendonca,
Caliber: 6R15B, 23 jewels
Caseback type: 6R15-00G0
Movement: Automatic, plus auxiliary hand winding and hacking
Beat rate: 21,600 bph (6 beats/sec)
Loss/gain: Less than 25sec/day
Power reserve: 50 hours
Calendar: Date only
Crown: Screw-in type
Construction: Stainless steel
Crystal: Hardlex glass, slightly domed profile
Bezel: Unidirectional, 120 graduations
W.R. rating: 200m, ISO certified
Luminous material: LumiBrite™
Movement Japan, cased in Japan
I wished that the 6R15 had the higher beat, 28,800 bph escapement that their defunct 4s15 offered but then the 6R15 wasn’t meant to directly replace the 4s15. A high beat design would have pushed the price higher and the 6R15 is based on the tried and proven, 7s platform with a larger main spring, hand winding and hacking thrown in for a good measure.
Personally, I like to draw a loose analogy of the SBDC001 diver to the BMW X3 sports utility vehicle and the SBDX001 Marine Master to the range topping X5 model, which BMW released much earlier. The X3 was introduced to buyers who want a more compact and more affordable Bimmer. If you’re already an X5 owner, you probably not want to buy the X3 – unless of course you’re a moneyed, serious BMW enthusiast. You’d rather spend on some other BMW model or make.
Above: The higher specified BMW X5 (left) and the cheaper and smaller BMW X3 (right)
In a similar vein, most SBDX001 Marine Master owners may not want a Sumo diver as the former is already the flagship mechanical Seiko diver (well, some guys own both the Marine Master and the Sumo). For what it’s worth, the Sumo diver is in a class of its own. It will certainly appeal to budget conscious Seiko enthusiasts who want a taste of a hand winding and hacking diver’s watch.
Top: A very nice wrist shot of the prestigious Seiko SBDX001 Marine Master over the breathtaking skyline of Hong Kong. Image courtesy of “Tintin". He actually owns both this watch and the SBDC001 Sumo diver.
Would I buy this watch again? Absolutely. For the asking price, the Sumo is a lot of watch for the money. Interestingly, it was noted that there was a temporary shortage of the SBDC001 model in late 2007 and the Japan based sellers like Higuchi and Seiya ran out of stock of this watch.
Unfortunately since 2008, prices of Seiko watches have gone up across the board. I was told this is due to rising costs of raw materials and the strong Japanese Yen currency against the US greenback.
The orange SBDC005 doesn’t appeal to me that much as it lacks black framed markers for added dial contrast. The blue SBDC003 has a shade that’s too bright for my taste (although many also like the blue Sumo), so I would definitely purchase the black SBDC001 again if I had to.
Nevertheless, beauty is in the eye of the beholder and no matter which color you choose, the Sumo diver makes a good selection for a mid-priced mechanical Seiko diver.
As a final word, the Sumo gets my personal vote anytime!
Above: Photo of my SBDC001 diver on my smallish 6.5 inch wrist.
What I liked:
- Interesting design elements, a mix of the old and the new
- Auxiliary and winding and hacking features
- Very bright and sensitive lume
- More accurate than the entry level 7s-caliber divers
- Longer power reserve (50 hours)
- Solid feel, high quality stainless steel
- Immaculately polished finish
- Very good value for the money
What I didn’t care for:
- Lugs could have been wider, at least 22mm to match the size of the case
- Standard beat rate of 21,600 bph
- Bracelet end pieces not flush with the lugs
- Watch may be too large for some people
- Average looking bracelet
- Date text is not perfectly centered
- Non-traditional bezel numbers
- Poor quality control in the earlier batches
||Value for money
Note: More orange boxes represent better scores.
This is my personal assessment of the reviewed watch and does not necessarily reflect the views of others.
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