At the beginning of the year, the Seiko Prospex series was relatively quiet.
In the brand's 145th year, we saw significant new releases in the King Seiko, Seiko 5 Sports, and Presage collections. However, new Prospex watches were limited to the Speedtimer, introduced right after New Year's. Today, the brand announces two new Prospex Marinemaster models that are sure to interest fans of Seiko dive watches. Both variants - the Prospex Marinemaster HBF001 and HBF002 - are updated versions of the modern interpretation of the 1968 diver. They feature new dials, an updated caliber, and a bracelet with a new clasp. In this review, we will examine all the innovations in detail.
History of the Seiko Prospex Marinemaster HBF001 and HBF002 Series Update
Less than a year and a half ago, Seiko updated the Marinemaster series with the SLA077 and SLA079 models, based on the classic reference 6159-7001, known as the 1968 diver. It was clear then that the brand would use the Marinemaster name for several designs. There are two Marinemaster series - one based on the 1965 diver, the other on the 1968 diver. The latter has now received updates, including a new caliber and a new bracelet with a tool-free micro-adjustment system, long awaited by fans. Let's take a closer look at both models.
Main Features of the HBF001 and HBF002 Models
Both new models feature a stainless steel case with a diameter of 42.6 mm, a thickness of 14.1 mm, and a lug distance of 49 mm. Water resistance is 300 meters, and the screw-down crown is located slightly above the 4 o'clock mark. The bezels on both models are steel but with ceramic inserts: black for the HBF001 and blue for the limited HBF002. The use of ceramics is an important update compared to previous models, which used steel inserts.
Both models are equipped with an updated five-row bracelet, whose design is similar to the previous generation. Despite its resemblance to the three-row bracelets of many dive watches, the narrow polished links are separate elements.
The main innovation is the folding clasp with a tool-free micro-adjustment system. It allows the bracelet to be extended by 16 mm in 2 mm increments. Conveniently, the extension can be removed directly on the wrist by simply pressing the clasp. The case and bracelet are coated with an ultra-hard composition for increased scratch resistance and comfortable daily use.
Mechanism Update: Seiko Caliber 8L45
The key technical innovation of both models is the proprietary Seiko caliber 8L45. This mechanism was already used in the anniversary Marinemaster SLA081 model last year and in several King Seiko Vanac models. The 8L45 caliber is Seiko's top development, operating at a frequency of 28,800 vibrations per hour, containing 35 jewels, and has a power reserve of 72 hours. It replaced the previous 8L35, used in modern interpretations of the 1968 diver.
Unlike the 8L35, based on the Grand Seiko 9L55 caliber, the 8L45 is based on the 9L65. Compared to its predecessor, the number of jewels increased from 25 to 36, accuracy improved from -10/+15 seconds per day to -5/+10 seconds, and the power reserve increased from 50 to 72 hours. The mechanism is hidden behind a steel case back, but it's important that Seiko chose the best modern caliber for these watches.
Limited Edition Seiko Prospex Marinemaster HBF002
The HBF002 is a limited edition of 1,000 pieces, created in collaboration with the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). The collaboration between Seiko and JAMSTEC has been ongoing since the early 1980s. The agency conducts marine research to advance science and technology. During expeditions, JAMSTEC staff use Seiko dive watches in extreme conditions to test their reliability.
One of the agency's projects is the Arctic research program. This year, the construction of Japan's first research vessel with icebreaking capabilities - Mirai II (未来, meaning "future") - will be completed. The vessel will allow data collection in icy seas. The design of the HBF002 is inspired by this vessel.
The model's dial has a textured pattern depicting the path of an icebreaker through sea ice. The vertical gradient is colored dark blue in the center and light blue around the edges. The dial is covered with a transparent polished lacquer to enhance the visual effect. The Marinemaster hands are filled with Lumibrite, and the second hand is in a gold color, adding an accent.
Design Features of the HBF002
- A white ring with dark blue minute markers around the dial highlights the bright design.
- A blue ceramic bezel with white markings harmonizes with the dial.
- Indices filled with light green Lumibrite.
- A date window with a frame located at the 3 o'clock position, date in black on white.
- A small luminescent marker next to the date ensures a complete set of glowing hour markers.
The model's aesthetics symbolize JAMSTEC's contribution to Arctic research and its significance for the future of science.
The HBF002 will be available in July 2026 at Seiko boutiques and selected stores for €4100.
Seiko Prospex Marinemaster HBF001 Model
The main model for a wide audience is the HBF001. Externally, it resembles its predecessor, but upon closer inspection, changes are noticeable. The new matte black dial features a date window at the 3 o'clock position instead of 4:30, improving visual balance. The numbers on the bezel are wider and in a more modern font.
The dial texture is similar to the previous model, and the indices are filled with Lumibrite, as in the SLA079. The inscription at the bottom now reads "Automatic 3 Days" instead of just "Automatic." These changes are minor but noticeably enhance the design.
The signature case shape with characteristic angular lugs and side facets remains - one of the best case designs in Seiko's history, appearing with the Marinemaster SDBX001 in 2000.
The HBF001 will be available from July 2026 for €3800 at official boutiques and selected stores.
Conclusion: Evaluation of the New Seiko Prospex Marinemaster HBF001 and HBF002 Models
We had the opportunity to test both new models, and they are truly impressive. Both models are large and solid but sit comfortably on a wrist with a diameter of 18.5 cm. These watches are not suitable for small wrists, but if you're used to 42 mm cases, the new Marinemasters are worth considering.
They represent the pinnacle of the Prospex collection. The visual updates make the design more balanced, the new clasp increases practicality, and the 8L45 caliber provides excellent accuracy and reliability for everyday use.
The price increase is justified by the improvements: if the previous SLA079 cost €3000, the HBF001 is priced at €3800. Other Marinemaster models based on the 1965 diver are around €3400. Considering the updates in design and mechanism, the price increase aligns with the model's position in the collection.
The new Marinemasters remain among the best Seiko dive watches and continue the traditions that made the series legendary among brand fans.
