Watch enthusiast and writer Shun Horiuchi reviews the Ref. SLGB015 from the "Evolution 9 Collection," updated in 2026, featuring a 37mm case and a dial with a stamped "water surface" pattern. During his one-week wear period, Horiuchi considered the current state of Grand Seiko as a luxury watch brand in terms of both "functional value" and "emotional value."
Photographs & Text by Shun Horiuchi
[Article published on January 4, 2026]
A deep dive into the "Evolution 9 Collection" Ref. SLGB015
Grand Seiko's "Spring Drive UFA (Ultra Fine Accuracy)," which achieves an astonishing accuracy of ±20 seconds per year, is attracting attention. This movement achieves this high precision in a standalone manner without receiving standard radio waves or GPS signals from external sources, making it highly practical for everyday use as it significantly reduces the frequency of time adjustments.
The Spring Drive UFA's "Evolution 9 Collection," featuring the newly developed "Caliber 9RB2," was updated in 2026. Among its lineup is the Ref. SLGB015, a model with a 37mm diameter Ever Brilliant Steel case and a bright navy blue dial. Considering its size, it could be a noteworthy option for users with slender wrists.
I previously wrote an in-depth article about Ref. SLGW007, which belongs to the same Evolution 9 collection.
The main differences between this model and the Ref.SLGW007 are twofold: firstly, it has a slightly smaller case size with a diameter of 37mm, but is somewhat thicker at 11.4mm; and secondly, it is equipped with the Spring Drive UFA Cal.9RB2 movement, compared to the hand-wound mechanical Cal.9SA4. Furthermore, this model features a bracelet instead of a strap.
Since the case design and basic exterior concepts are common, this article will minimize redundant explanations and focus on reviewing the unique features of this model: the comfortable fit of the 37mm diameter case and the practicality provided by the Cal.9RB2 movement.
This new Grand Seiko model features a Spring Drive UFA movement that achieves an accuracy of 20 seconds per year. The dial, with its distinctive stamped pattern, is a bright navy blue, evoking the image of soft morning sunlight reflecting off a lake surface rippling in the wind, creating a sparkling scene. Automatic Spring Drive (Cal. 9RB2). 34 jewels. Power reserve of approximately 72 hours. Stainless steel case (diameter 37.0mm, thickness 11.4mm). 10 ATM water resistance. 1,386,000 yen (including tax).
Outline of Ref.SLGB015
The case design of the Evolution 9 collection combines the strength and sharpness characteristic of Grand Seiko, exemplified by its robust exterior components. Looking at the case side, particularly from the 3 o'clock or 9 o'clock position, one can see that the basic structure, without the lugs and bezel, is close to a cylindrical shape. The lugs don't droop too low, and the case side lines curve in a large arc, adding to the cylindrical case body. The presence of polished surfaces near the inside of the lugs gives a delicate impression. The top of the case features a fine vertical hairline finish, and a separate bezel with a polished outer edge is attached. The box-shaped sapphire crystal rising from this bezel creates a three-dimensional silhouette.
Comparing this model to the previously discussed Ref.SLGW007, there are, as mentioned before, two major differences. First, the case diameter has been reduced to 37mm. Second, it is equipped with the automatic Spring Drive UFA Cal.9RB2 instead of the hand-wound mechanical Cal.9SA4. Primarily due to the difference in the movement, the case thickness is slightly thicker than the Ref.SLGW007 at 11.4mm. The Cal.9RB2 is 5.02mm thick, which is about 0.9mm thicker than the Cal.9SA4's 4.15mm. As a result, one might expect the overall form to have a rounded appearance, but this is not the case. Rather, the design codes of the Evolution 9 collection have been maintained while making subtle adjustments, resulting in the sharp case form that is characteristic of this collection.
While the 37mm diameter might suggest a small watch, the thin bezel and wide dial give it a surprisingly large visual presence. At the same time, it fits comfortably on the wrist, suggesting that this Grand Seiko model prioritizes wearability, even more so than many recent models.
This model shares its basic specifications with the Ref.SLGB003, which was unveiled at Watches & Wonders Geneva in 2025. The main differences are that the case and bracelet material has been changed from bright titanium to ever-brilliant steel, and the dial has been redesigned to a lighter navy blue "water surface" pattern.
What about the details?
Now let's take a look at the details.
The case shape is as described in the previous section, and the design of the indices and hands is basically the same as the Ref. SLGW007, which we previously looked at in depth. The sharp edges created by the multi-faceted cuts and the distortion-free polished finish are still present, and there is almost no room for criticism regarding its level of perfection.
The first thing that catches the eye is the navy blue dial with a "water surface" pattern. In brightly lit environments, it displays a vivid blue, while in everyday indoor lighting, it appears as a deep navy blue, almost black. It is neither gaudy nor ostentatious. Considering its nature as a practical timepiece, this color scheme is skillfully chosen. The dial design is largely the same as that of the Evolution 9 Collection Ref. SLGA021, a 40mm case diameter model released in February 2023. The "water surface" pattern used on the dial represents the ripples spreading across the surface of Lake Suwa, located southeast of the "Shinshu Time Craftsman Workshop" within Seiko Epson's Shiojiri Plant, where Grand Seiko's Spring Drive models are manufactured. This is created by stamping a mold with the pattern hand-carved by craftsmen, and the navy blue represents the shimmering surface of the lake illuminated by the morning sun.
The bezel is relatively slender compared to the overall form, which gives the impression that the dial is larger than the actual 37mm diameter case size. It certainly doesn't feel small. The hairline finish on the case sides and the tops of the lugs is extremely delicate and beautiful. The contrast with the polished surface of the lug shoulders that breaks up the hairline is also beautiful. Although only the top is visible due to the presence of the flash fit, the case sides between the lugs, which are difficult to polish, are also finished to a high standard.
Looking at the side of the case, this model employs a structure where the lug holes go all the way through. I didn't pay much attention to this with the strap model Ref. SLGW007, but this model, which comes with a bracelet, also has a similar through-hole in the first link on the case side, which may be a point of interest for some people. It's not a matter of good or bad, but if you prioritize appearance alone as a luxury watch, you might prefer the closed-hole design.
Next, let's look at the bracelet. Thin, separate parts are incorporated on either side of the central links, and although it appears to be a three-row configuration when viewed from the front, it is actually a five-piece structure. This design seems to be intended to create a visual sense of three-dimensionality, but on the other hand, the links on the flash fit and buckle side are a single piece, so the connection lines between these separate parts and the links are represented by engraved lines, leaving a slight sense of incongruity from the perspective of design continuity.
While the hairline finish on the surface is beautifully done, the finishing on the sides of the links doesn't seem as meticulous as the case.
The buckle is a robust structure made from a collection of machined parts, and some parts are made of bright titanium. The practical 2mm increment x 3-step fine adjustment mechanism has a good feel to it, and the buckle's fastening method and spring feel are appropriate and reliable. The contrast between the polished and blasted finishes is beautiful, and the GS logo is impressive, showing attention to detail.
This sturdy and robust buckle achieves a good balance in terms of thickness and weight with the watch case, which is 11.4mm thick. However, personally, I felt that the bracelet links themselves could be a little thinner, which would improve the wearing comfort. I will elaborate on this point later.
A movement that Grand Seiko fans will covet.
The movement features the Spring Drive UFA Cal.9RB2, which achieves an accuracy of ±20 seconds per year.
For Grand Seiko fans, the name "UFA" likely brings to mind the Grand Seiko "VFA (Very Fine Adjusted)" that debuted in 1969. While the VFA pursued the limits of manual adjustment techniques to achieve high precision, the UFA is interesting because it combines modern electronic control technology with advanced watchmaking techniques.
To achieve an accuracy of ±20 seconds per year (equivalent to an average monthly deviation of ±3 seconds), the quartz oscillator used is the same as that used in the 9F quartz movement, having undergone an aging process to ensure stability. In addition, it is equipped with a "high-precision Spring Drive package IC" that contains an ultra-low-power IC with a temperature compensation function to correct for accuracy changes due to temperature, sealed in a vacuum package. In other words, temperature compensation is completed within this IC. Furthermore, a speed regulator switch is installed to compensate for the slight changes in the quartz oscillator's oscillation frequency over time, which are caused by the slight strain remaining in the quartz oscillator after manufacturing. During after-sales service, the accuracy can be finely adjusted to match the movement's characteristics, making it possible to maintain annual accuracy over a long period of time.
In addition, a thin single barrel and a new offset magic lever were developed and incorporated to lower the movement's center of gravity, resulting in a power reserve of approximately 72 hours. The fact that "lowering the movement's center of gravity" was included in the development philosophy is particularly noteworthy. This is precisely what you would expect from a vertically integrated manufacture.
This movement also prioritizes aesthetics, reflecting the brand philosophy of "THE NATURE OF TIME." To represent the frost found in the sub-zero temperatures of the Shinshu region, the surface of the bridges has been given a matte finish. This matte finish makes the diamond-cut surfaces around the jewel holes sparkle beautifully. Furthermore, the rotor is hollowed out all around, making the power reserve indicator easy to read regardless of its position. The bidirectional automatic winding mechanism utilizes Seiko's traditional Magic Lever for efficient winding.
While it's not a movement that overtly emphasizes flashy ornamentation, considering its worldview and technical background, its appearance is fitting for this timepiece.
Wearing impressions
The unit I borrowed this time was a sample model, but I actually wore it for about a week.
First, I'd like to discuss the watch's most distinctive feature: the Spring Drive UFA. During this trial period, there was virtually no visible error. Of course, this is a sample watch, and it's impossible to comment on its annual accuracy after only about a week of wear, but its behavior was remarkably stable, almost like a radio-controlled watch.
Furthermore, with a power reserve of approximately 72 hours, the watch hands will not stop even over a two-day weekend, making it exceptionally practical. For users who demand high practicality from their watches, this peace of mind is a huge advantage, making it a very attractive option for those who value practicality.
Next, let's talk about how it feels to wear.
The 37mm case diameter is relatively small for a recent Grand Seiko. However, the large dial area gives it a visual presence that is greater than the numbers suggest. On the other hand, the lugs fit well, and I felt that this model offers a high level of wearability, especially for users with slender wrists, compared to other models in the current lineup.
However, the impression you get when wearing them isn't necessarily "light and airy."
While a case thickness of 11.4mm is by no means extremely thick, the watch as a whole possesses a presence and weight that belies its appearance. The Ref. SLGW007, which we previously explored in depth, achieved a case thickness of less than 10mm, and still felt superior in terms of its low center of gravity and agility.
Of course, a direct comparison is impossible since they use different movements, but lowering the center of gravity was one of the key themes in the development of the Cal.9RB2. Knowing this philosophy, it's true that when you wear it, you can't help but expect an even greater level of lightness and agility.
If you were to make it even thinner, you would need to comprehensively reduce the thickness of the dial, the hands and indices, the clearance between the hands, the clearance between the case back and the movement, and the thickness of the sapphire crystal on the case back. However, reducing these dimensions, especially around the gaps between the hands, makes maintenance more difficult. So the question becomes where to draw the line, but conversely, it is precisely by overcoming these difficult challenges that the technical skill of a luxury watch manufacturer is put to the test.
I have no complaints about the overall quality of the bracelet and buckle. They have a robust construction and high precision, and the fine adjustment mechanism is very user-friendly. However, I personally questioned whether such a heavy bracelet was really necessary.
In recent years, the value demanded of luxury watches has expanded beyond mere weight and robustness. Factors such as how well the watch conforms to the wearer's body, how it feels integrated with the wrist, and how comfortable it is to put on and take off are also becoming increasingly important. While this watch's bracelet possesses a solid and robust construction, it also seems to strongly reflect a design philosophy that prioritizes weight and robustness.
On the other hand, I was particularly impressed with the bracelets of Credor, another high-end watch brand under Seiko Watch, especially the "Kuon" series. The revived "Credor Locomotive" bracelet also skillfully reproduces the original's distinctive rattling sound, achieving a balance between luxury and a comfortable looseness. I would certainly like to see a similar approach taken with Grand Seiko's bracelets.
Overall, the Ref. SLGB015 is a model that combines outstanding practical performance with an annual accuracy of ±20 seconds with excellent wearability thanks to its 37mm diameter case. On the other hand, I felt that Grand Seiko will need to offer more than just functionality, but also propose new wearing experiences.
Summary and Grand Seiko's current position
The "Evolution 9 Collection" Ref.SLGB015 that we tested this time is the latest regular model, featuring a Spring Drive UFA movement boasting an astonishing accuracy of ±20 seconds per year, fitted to a modern 37mm case size.
For users with particularly slender wrists, this 37mm diameter size is especially significant. While recent Grand Seiko models have mainly featured cases around 40mm in diameter, this model strikes an excellent balance between wearability and presence, making it an attractive option as a practical everyday watch.
Furthermore, the performance of the Cal.9RB2, with an annual deviation of ±20 seconds, cannot be overlooked. Rather than simply competing on specifications, I felt that this represents a fundamental evolution as a practical timepiece, as it minimizes the everyday act of "setting the time" that is necessary with a wristwatch.
On the other hand, this device has given me something to reconsider.
In recent years, significant advancements in machine tools and processing technology have led to a substantial improvement in exterior quality across the entire watch industry. Even in areas where Grand Seiko once held a dominant position, many manufacturers, including Swiss and German companies, are rapidly catching up. The quality improvements of mid-range brands, in particular, have been remarkable, and I am often surprised by the quality of their new releases.
Of course, the perfection of Grand Seiko's hands and indices, as well as the richness of its dial design, should still be highly praised. In particular, the stamped dials featuring nature motifs have now firmly established themselves as an iconic element of the brand.
Furthermore, what I hope for from Grand Seiko in the future is not just further improvements in functionality and quality.
For example, there are subjective values that are difficult to quantify, such as how they feel when worn, the design of the bracelet, or the atmosphere created by the metal parts.
When you encounter excellent Swiss or German watches, you sometimes feel an appeal that is difficult to explain logically. It may stem from their history and culture, or it may be an aesthetic sense that has been accumulated over many years.
If I had to describe it in one word, it would be "sex appeal."
The Ref.SLGB015 is already an extremely high-quality timepiece in terms of functional value. That's precisely why it prompts us to reconsider the question of where Grand Seiko should aim to go next.
Akio Naito, President and CEO of Seiko Watch Corporation, said, "From functional value to emotional value."
I will be watching with interest to see how Grand Seiko will demonstrate part of the answer to this question in the future.
