The Seiko Marinemaster Professional SBEX001 is a 2015, 700-piece anniversary diver built around a rare combination: a 36,000-vph automatic movement, a one-piece titanium case and a 1,000m saturation-diving specification. Its 48.2mm diameter and 19.7mm thickness make it an imposing watch even though titanium keeps its weight in check. Seiko introduced it to mark 50 years of its diver watches; it is best understood today as a historically specific collector’s model, not as a current-production offering.
What the SBEX001 is—and why Seiko made it
Seiko announced the SBEX001 in 2015 as a limited Prospex model commemorating 50 years since its first diver watch, introduced in 1965. The Japanese release date was June 6, 2015, and worldwide production was limited to 700 pieces. Seiko positioned it as a mechanical Hi-Beat 36000 watch for 1,000m saturation diving, rather than simply a large anniversary-style sports watch. Seiko’s 2015 announcement is the primary source for its release specifications.
The model’s appeal rests on the tension between technical purpose and collector interest: a professional-diver specification, a high-frequency movement and a construction that avoids a conventional removable caseback, all wrapped in a limited anniversary release. Those details describe the watch’s original design and launch, not the present condition or value of any example offered for sale.
SBEX001 specifications
| Specification | SBEX001 |
|---|---|
| Release | Japan, June 6, 2015; worldwide limited edition of 700 pieces, according to Seiko’s 2015 announcement. |
| Movement | Seiko automatic/manual-winding caliber 8L55; 37 jewels; 36,000 vibrations per hour (10 beats per second); approximately 55-hour running time, per Seiko’s 2015 specification. |
| Accuracy specification | +15 to −10 seconds per day under Seiko’s stated 5–35°C conditions at launch. |
| Case | One-piece titanium case with DiaShield surface treatment; 48.2mm diameter and 19.7mm thick, excluding button protrusions, per Seiko’s launch specification. |
| Water resistance | 1,000m saturation-diving specification, per Seiko’s 2015 announcement. |
| Dial and crystal | Black dial; anti-fog-treated sapphire crystal, per Seiko’s 2015 announcement. |
| Bracelet and included accessory | Titanium bracelet with DiaShield and a reinforced silicone replacement band included at launch. |
| Other listed features | Screw-lock crown, unidirectional rotating bezel, double-lock clasp with diver adjustment, and JIS Class 2 enhanced magnetic resistance, per Seiko’s launch specification. |
| Japanese launch price | ¥650,000 plus tax, Seiko’s recommended retail price in Japan in 2015; this is not a current market valuation. |
| European launch price | Approximately €6,400, the recommended retail price cited in Seiko’s 2015 international press material; this is not a current market valuation. |
Case and wearing profile: large, but titanium
At 48.2mm across and 19.7mm thick, the SBEX001 has dimensions that will dominate many wrists. The diameter alone does not tell the whole story: its height and substantial one-piece case give it a tall, purposeful profile, so sleeve clearance and how the watch sits on your wrist matter as much as the headline width. Seiko’s stated diameter and thickness exclude button protrusions.
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- STAINLESS STEEL: features a durable 43.8mm stainless steel watch case and bracelet.
- LUMIBRITE DISPLAY: this men's automatic watch features a highly-legible display with LumiBrite hands and markers
- 4R35 CALIBER: equipped with the reliable caliber 4R35 automatic movement, this accurate men's watch keeps precise time
The titanium construction is the counterweight to that scale. The case and bracelet use DiaShield-treated titanium, and contemporary watch journalist JX Su described the material as tempering the feel of the large case. That does not make the watch small or discreet; it means the listed dimensions should not be mistaken for the weight of a comparable steel watch. Su also noted that the bracelet attaches with screws.
The one-piece case has no conventional caseback, as Su observed in a 2015 hands-on account. That construction is part of the watch’s saturation-diving identity, but it also means a buyer should use a qualified watchmaker familiar with the model for service rather than treating it like an ordinary screw-back diver. The original design includes a screw-lock crown, a unidirectional bezel and a double-lock clasp with diver adjustment.
The 8L55: a 36,000-vph movement with a 55-hour reserve
Inside is Seiko caliber 8L55, an automatic movement that can also be wound by hand. At 36,000 vibrations per hour—or 10 beats per second—it runs at a high frequency, while Seiko listed approximately 55 hours of running time and 37 jewels. Its launch accuracy specification was +15 to −10 seconds per day under the company’s stated temperature conditions of 5–35°C; that is a factory specification, not a claim about the timekeeping of an individual watch today.
Rank #2
- WATER-RESISTANT: these water-resistant men's dive watches are ISO scuba-approved to depths of 200 meters
- AUTOMATIC: these self-winding, automatic men's watches are powered by your movement, with a power reserve of 41 hours
- STAINLESS STEEL: features a durable stainless steel watch case and coordinating silicone watch band
- LUMIBRITE DISPLAY: this men's automatic watch features a highly-legible display with LumiBrite hands and markers
- 4R36 CALIBER: equipped with the reliable caliber 4R36 automatic movement, this accurate men's watch keeps precise time
Seiko said the 8L55 was based on the diver-specific 8L35 and redesigned for the one-piece case. In its Japanese release, the company described the new movement as intended to improve resistance to external disturbances, including shock and vigorous movement, while providing stable precision. Seiko also said its proprietary mainspring and hairspring materials supported the combination of high beat rate, extended reserve, magnetic resistance and shock resistance. The movement was hand assembled and adjusted at the Shizukuishi High-End Watch Studio, according to the same release.
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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteThe headline rate is technically notable, but it should not be read as a guarantee of superior real-world accuracy in every example. The published figure is Seiko’s launch specification; actual performance depends on the condition, regulation and service history of the specific watch.
Dial and design cues
JX Su described the SBEX001’s dial as black gilt and traced its inspiration to Seiko’s 1968 300m Hi-Beat diver. That is the journalist’s design reading, rather than terminology Seiko used in its launch specifications. Su characterized the overall effect as a blend of vintage cues and modern case proportions: a historically referential dial set in a much larger, contemporary saturation-diver body.
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- WATER-RESISTANT: these rugged stainless steel dive watches for men feature a deep blue silicone strap and are both stylish and robust, following ISO standards for scuba, and are water-resistant to 200 meters
- 4R36 CALIBER: equipped with the reliable 4R36 caliber, these precise men’s wrist watches ensure the most accurate timekeeping
The anti-fog-treated sapphire crystal and black dial are the manufacturer’s listed details. The combination of a dark, high-contrast face and the broad case helps the watch read as an instrument, while the titanium finish and anniversary context give it a more specialized identity than a generic oversized diver.
What the 1,000m saturation-diving rating means here
Seiko specified the SBEX001 for 1,000m saturation diving. That is a design and rating claim for this model; it should not be confused with a published test of the SBEX001 itself. Seiko’s announcement separately cited a September 2014 test in which a 1,000m-rated Seiko saturation-diving watch was attached to JAMSTEC’s Kaiko 7000II unmanned submersible and confirmed operating beyond 3,000m. The announcement does not identify that tested watch as the SBEX001, which was announced the following year.
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For everyday ownership, the rating is most useful as evidence of the watch’s intended engineering brief, not as an invitation to expose an older example to extreme conditions. Water resistance can be affected by age, impact, gasket condition and prior service. Any real-world water use should depend on an appropriate, current pressure test performed by a qualified service provider.
Rank #4
- WATER-RESISTANT: these water-resistant men's dive watches are ISO scuba-approved to depths of 200 meters
- AUTOMATIC: these self-winding, automatic men's watches are powered by your movement, with a power reserve of 41 hours
- LUMIBRITE DISPLAY: this men's dive watch features a highly-legible display with LumiBrite hands and markers
- STAINLESS STEEL: this diving watch for men features a stainless steel watch case and bracelet, a uni-directional rotating elapsed timing bezel, and a bold blue dial evoking signature PADI colors
- 4R36 CALIBER: equipped with the reliable caliber 4R36 automatic movement, this accurate men's watch keeps precise time
Launch price and buying a discontinued SBEX001
At launch in 2015, Seiko listed a Japanese recommended retail price of ¥650,000 plus tax. Its international press material cited an approximate European recommended retail price of €6,400. These are historical launch prices, in different markets and tax contexts; they do not establish what the watch is worth or what a seller should charge now.
Current inventory, regional availability and condition-specific resale values are not established here. If considering an example, assess the particular watch rather than extrapolating from its limited-edition status. Useful checks include:
- Confirm the serial and edition documentation, and check that the watch is consistent with a 700-piece release.
- Verify authenticity with a specialist or authorized service channel where available; do not rely on photographs alone.
- Inspect the DiaShield-coated case and bracelet for wear, damage or mismatched parts.
- Ask for service records and a current water-resistance test if water use matters to you.
- Check completeness, including the reinforced silicone replacement band supplied with the watch at launch.
- Read the seller’s return terms and confirm what is included before payment.
As a large, 19.7mm-thick watch, fit should be considered in person if possible. If that is not practical, ask for clear wrist photographs and measurements, and make sure the return policy gives you a way to assess comfort after delivery.
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Best Value
- WATER-RESISTANT: these water-resistant men's dive watches are ISO scuba-approved to depths of 200 meters
- AUTOMATIC: these self-winding, automatic men's watches are powered by your movement, with a power reserve of 41 hours
- LUMIBRITE DISPLAY: this men's dive watch features a highly-legible display with LumiBrite hands and markers
- STAINLESS STEEL: features a durable stainless steel watch case and bracelet, unique case shape resembling teeth, and PADI red and blue colors on its elapsed timing bezel
- 4R36 CALIBER: equipped with the reliable caliber 4R36 automatic movement, this accurate men's watch keeps precise time
Who the SBEX001 makes sense for
The SBEX001 is a strong fit for a collector specifically interested in Seiko’s diver-watch history, the 1965 anniversary connection, or the unusual pairing of a 36,000-vph caliber with a 1,000m saturation-diving specification. Its titanium case and bracelet offer a lighter alternative to a similarly imposing steel watch, while the 700-piece production limit gives the model clear historical scarcity.
It is less suitable for someone seeking a compact daily diver, an easy fit under a cuff, or a watch whose current market price and availability can be assumed from launch-era figures. The central trade-off is straightforward: a technically distinctive, historically specific Seiko in a very large format, with the extra diligence that comes with buying a discontinued mechanical watch.
Source notes
Launch specifications, edition size, Japanese price, movement details and the anniversary framing are from Seiko’s 2015 Japanese announcement. The approximate European launch price is from Seiko’s 2015 international press material. Design observations and the case and bracelet description are attributed to watch journalist JX Su’s contemporary 2015 hands-on report.
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