5 minutes

Chrono24 Buyer’s Guide: Seiko Prospex SBDX001

By René Herold
You can find more reviews, how-to videos, talks, interviews, and other content related to luxury watches on our YouTube channel.

The Seiko Marinemaster 300 SBDX001 is a very popular diver among Seiko fans as well as those with a soft spot for diving watches. First introduced in 2000, the watch clearly shares a lineage with Seiko’s iconic divers from the 1960s, particularly the refs. 6215-7000 and 6159-7000. Seiko more or less copied the shape of the hands and indices, the hefty 44-mm monobloc case, and the crown at 4 o’clock from the historic models. The fresh, retro design stands out from the crowd of monotonous diving watches à la the Rolex Sub – not to mention the value for money is significantly better. 

Seiko Prospex Marinemaster 300 SBDX001: The Specs 

As a member of the Prospex collection, the Seiko SBDX001 is equipped with state-of-the-art technology. The caliber 8L35, which is based on the Grand Seiko caliber 9S55, powers the timepiece, offering a 50-hour power reserve and date display. Thanks to the screw-down crown and monobloc case construction, the watch is water-resistant to 300 m (30 bar, 984 ft). It is also suitable for saturation diving, despite not having a helium escape value due to the case design. Since the midsection and case back are a single, continuous unit (i.e., the case back cannot be opened), it is much more difficult for helium molecules to enter the watch. Of course, this also means the movement can only be accessed from the front. Thus, the bezel, glass, hands, and dial must be removed before servicing. 

The Seiko Prospex Marinemaster 300: Design 

The Seiko Prospex Marinemaster 300 SBDX001 is a tool watch through and through. Measuring 44 mm across and standing more than 15 mm tall, this watch will hardly slip under your cuff, but there is no denying it is a robust timepiece that exudes a strong presence. 

The dark dial is highly legible even in poor lighting conditions thanks to the applied hour markers that are filled with LumiBrite, Seiko’s own luminous material. The brand opts for bar indices at 6 and 9 o’clock, a double bar at 12, and dot indices for the remaining hours. The date display takes the place of the hour marker at 3 o’clock. The broad baton-shaped hands are coated in luminous material, as is the wide tip of the second hand. 

The Seiko Prospex Marinemaster 300 SBDX001 boasts a hefty monobloc case.

As you’d expect from a diving watch, the unidirectional bezel can only be turned anti-clockwise and features a 60-minute scale. A luminous dot marks the zero. The bezel inlay is made of aluminum and coated with a transparent lacquer. This gives it the appearance of ceramic, but is unfortunately much more prone to scratches. Seiko equips the watch with its own Hardlex mineral glass, which is likewise slightly more prone to scratches than sapphire glass but, in turn, does not shatter.  

You can find this watch on a silicone strap or three-piece link stainless steel bracelet. The latter features a safety clasp with a diving extension system, meaning you can easily adjust the length of the strap without any tools.  

SBDX001: A Sought-After Collector’s Item 

The Seiko Marinemaster 300 SBDX001 was initially launched exclusively on the Japanese market, making it a JDM, or Japanese domestic market, model. It wasn’t until 2012 that the timepiece found its way to European markets. As a result, it is far less common to find new or well-maintained examples in Europe, the Americas, or the Arab region than in Japan. 

Prices for a new Seiko SBDX001 have remained relatively stable between spring 2021 and 2022, ranging from $2,300 to $2,700. Used watches aren’t far off, costing around $2,500 on average. It will be interesting to track how the value of this timepiece develops over the coming months and years. While Seiko stopped producing this reference in 2015, demand remains high. As of the time of writing, the trend certainly seems to be heading northwards. 

Performance of the Seiko Marinemaster Ref. SBDX001

Alternatives to the Seiko SBDX001 

Considering the ref. SBDX001 was such a big hit for the brand, it’s not surprising that the Japanese watch giant has released a number of different variants over the years. Two references that are particularly popular among collectors are the Seiko SBDX003 and SLA025

The former was released at the same time as the SBDX001 and is technically identical, but features gold-colored hands and indices in keeping with the original 1960s look. This timepiece has a limited run of just 500 pieces, making it an extremely rare find, which is certainly reflected in the market price. Expect to pay between $3,800 and $5,400 for this timepiece on Chrono24. 

The SBDX003 – limited to just 500 pieces
The SBDX003 – limited to just 500 pieces

The SLA025 looks strikingly similar to the SBDX003 at first glance, but upon closer inspection, you’ll notice that the bezel numbers on this reference are likewise in a gold tone. This watch is powered by the Hi-Beat caliber 8L55, which beats at 36,000 vph, offering improved accuracy. Despite the high balance frequency, the movement still has an impressive power reserve of 55 hours. The SLA025 was launched in 2018 in a limited run of 1,500 pieces. New watches change hands for around $4,600 on Chrono24. 

If you prefer the simpler look of the Seiko Marinemaster SBDX001, be sure to check out its successor model, the ref. SBDX017. This timepiece is nearly indistinguishable from its predecessor, both in terms of visuals and specs. The only differences are the “Diashield” protective case coating and the Prospex “X” on the crown. Prices for the ref. SBDX017 run around $2,500 for a new watch and $2,000 for a used one. 

The Current Seiko Marinemaster 300 

The latest edition of the Seiko Marinemaster 300 is the ref. SLA021, which is sold under the reference number SBDX023 in Japan and Southeast Asia. While the dimensions of the timepiece were left untouched, it gained a ceramic bezel inlay, sapphire crystal, and a golden second hand. Much to the disappointment of many Seiko fans, the Marinemaster inscription on the dial has also been replaced with the Prospex logo. Set aside roughly $2,900 to call an unworn SLA021 your own. Pre-owned models in good condition are closer to $2,000. 

Seiko also introduced two more colorful Marinemaster 300s to the range with the refs. SLA023 and SLA047. The SLA023 features a blue dial and the SLA047 a green one. In terms of cost, expect to see prices between $2,400 USD and 3,000, depending on the exact model and the watch’s condition. 

About the Author

René Herold

My name is René Herold, and I first discovered Chrono24 in a job listing. Admittedly, I didn't really care about watches before coming to Chrono24. However, after a few …

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