9RB2 Caliber - Grand Seiko's revolutionary movement accuracy

Pushing the boundaries has always been at the core of every aspiring watchmaker. The most successful ones, whose portfolios are marked by revolutionary breakthroughs, never rest on their laurels. Grand Seiko constantly proves that it's the rightful member of such an elite group. Recently, they introduced the 9RB2 Caliber, a movement with a groundbreaking accuracy of ±20 seconds per year. No, it's not a typo; it does say ±20 seconds per year.

Grand Seiko has always prioritized accuracy as the primary goal since its founding in 1960. The first major breakthrough happened in 1969, with the introduction of the V.F.A. line. Some models from this series could be adjusted to an astonishing precision of ±2 seconds per day. Fast forward to April 2025, the U.F.A. Spring Drive caliber, and the unimaginable ±20 seconds per year. Let's examine what it took to reach another revolutionary milestone in accuracy and what makes it possible for the 9RB2 caliber to raise the bar to unprecedented heights in terms of accuracy in mainspring-powered mechanisms.

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Historical Significance: From V.F.A. to U.F.A.

Back in 1969, the acronym V.F.A. (Very Fine Adjusted) announced something unheard of before: a mechanical movement adjusted to an exceptionally high level of precision, with a tolerance of ±1 minute per month, which far exceeded the standard Grand Seiko watch variations and was an astonishing achievement. Over the next couple of years, all GS production revolved around V.F.A., while, in parallel, GS engineers continued to work on improving accuracy. Finally, in 1975, V.F.A. was discontinued, giving way to the more precise Seiko Superior quartz watch, which achieved a monthly accuracy of ±1 second.

However, the GS team again did not let success lull them and has continued to work on improving the accuracy of their mechanical movements. Grand Seiko reintroduced the V.F.A. in 2018 for a limited-edition mechanical watch powered by a 9S85 Hi-Beat movement with an accuracy of +3/-1 seconds per day. And, finally, a couple of months ago, a breakthrough that seemed unattainable was achieved: the U.F.A. and its world record in accuracy when it comes to mechanical movements.

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U.F.A. (Ultra Fine Accuracy) depicts GS Spring Drive movement Caliber 9RB2, a mechanical marvel that has redefined the boundaries of mechanical timekeeping precision. U.F.A. presents a clear homage to its infamous predecessor and an ultimate proof of how the enormous effort invested in the relentless pursuit of accuracy perfection over the last 56 years paid off. U.F.A. is 36 times more accurate than V.F.A., which is understandable from the perspective that more than half a century of development and hard work separates the two. However, the 9RB2 Caliber is nine times more accurate than Grand Seiko's next most accurate movement, the Caliber 9R86.

What led to such awe-inspiring figures?

Engineering Marvel - The 9RB2 Caliber

9RB2 is an in-house movement based on the same fundamentals as the entire 9RA series of movements, featuring a quartz oscillator that has undergone a three-month aging process and an ultra-low-power integrated circuit with temperature-compensating capabilities. While brainstorming the idea of crafting a caliber that can significantly surpass the accuracy of their current calibers, the engineering team of GS has meticulously gone over their processing and manufacturing methods with one thought constantly going through their minds, how to minimize external impacts on the operation of the crystal oscillator coming from temperature changes and followed by gravity, and humidity, to name just a few.

Now, what did they come up with that made a nine-fold advancement over the renowned movements of the 9RA series? There are three game-changing factors:

• Vacuum-sealed technology that protects against environmental interference

The influence of external factors is the number one negative impact on the accuracy of a watch mechanism. The key to achieving such accuracy with 9RB2 is minimizing temperature differences within the integrated circuit, thereby attempting to eliminate the influence that temperature changes have on the frequency of the quartz oscillator. The revolutionary touch turns out to be the vacuum sealing of the oscillator and the temperature-measuring sensor within the integrated circuit.

Since the frequency of the quartz oscillator is significantly influenced by fluctuations in temperature, Caliber 9RB2 utilizes a temperature sensor integrated within its special silicon-on-insulator integrated circuit (SOI-IC) to gather information about temperature 540 times a day. All to monitor the impact of temperature changes within the IC, and regulate the oscillator’s performance. That's why placing the IC and the crystal oscillator within a single vacuum-sealed area enables extremely accurate temperature adjustments and virtually eliminates temperature differences between the two.

Finally, since all connecting wiring between the IC and the oscillator is also within the said vacuum-sealed area, it also stops the potential influence of humidity, static electricity, and light.

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• Individual thermo-compensation programming - making each watch literally unique

Precise measuring and data implementation play a crucial role before vacuum-sealing the oscillator and the integrated circuit. This involves diligently measuring the frequencies of each individual oscillator at different temperatures and then programming that data into the IC, which is specifically designed for that watch. All that happens after a three-month aging process that each individual quartz oscillator undergoes.

Next, data collected from measurements and programmed into the integrated circuit enables its temperature sensor to calculate the influence of various temperatures on the operation of the quartz oscillator. Upon such calculation, the integrated circuit compensates for any temperature differences and corrects potential frequency variations in the oscillator's operation. By doing so, it ensures stable and accurate operation regardless of any temperature variations. That means that practically any watch using Caliber 9RB2 is uniquely programmed, depending on the environment in which it is used, which ensures that the accuracy of ±20 seconds per year is consistent worldwide.

• The breakthrough regulation switch for lifetime precision maintenance

The Caliber 9RB2 is the only Spring Drive movement that features a regulation switch whose function is to correct time gain and loss. It fixes those minute deviations in accuracy that are influenced by fluctuations in oscillator frequency over prolonged use. The regulation switch can be used during regular checkups or for any after-sales service. What this means in practice is that Caliber 9RB2's world record accuracy is secured before its installation in a watch and remains regulated throughout the watch's operation.

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Manufacturing Artistry of Caliber 9RB2

The discussion about Spring Drive and quartz watches of Grand Seiko simply cannot go without mentioning the Shinshu studio's role. Once again, the engineering team working in this infamous studio played a crucial role in brainstorming, crafting, engineering, and manufacturing of Caliber 9RB2. 9RB2 is the fusion of mechanical soul with quartz precision. The manufactured parts, after undergoing a unique preparation process, are assembled and finished by hand, with components individually calibrated.

Some of the authentic craftsmanship touches that make Caliber 9RB2 unique include redesign of the Offset Magic Lever to fit a single barrel, reconceiving the width and length of the mainspring, barrel volume ratio, and thickness in order to facilitate a 72-hour power reserve and achieve a lower center of gravity for improved wearability. Hand finishing is inspired by the environment around the Shinshu studio. The jewels installed, the mirror polished and beveled edges, and the subtle texture of movement's surface all radiate the unique aesthetics of the nature surrounding the studio.

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To complete the picture of the manufacturing artistry of the Caliber 9RB2, its single mainspring barrel and a one-piece center bridge allow for a thin profile and a small diameter of just 30mm by 5.02mm. Additionally, the Caliber 9RB2 features authentic antimagnetic shielding. It's divided into 4 sections positioned on both sides of the movement's clearing space. The result of all these listed features is a smaller movement that retains its exceptional performance.

Caliber 9RB2 can fit in a watch with a case as small as 37mm. Given the features of this Caliber, it's another groundbreaking achievement of the Shinsu engineering team's craftsmanship.

Precision adjustments carried out during after-sales service, tailored to caliber characteristics, guarantee a superb annual rate over many years. Also notable is the use of magnetic resistance, which reduces the influence of magnetic effects and facilitates miniaturization. While the conventional approach is to place a soft-iron magnetic ring around the movement’s perimeter, Caliber 9RB2 divides this shielding into four sections placed strategically in the movement's clearance spaces on both sides. Such continuous refinements in conception and technology deliver a smaller movement that maintains exceptional performance.

Industry disruption in light of Caliber 9RB2 achievements

Caliber 9RB2's appearance raises a series of questions that yet remain to be answered. With its record-breaking accuracy, it is clear that the traditional mechanical accuracy standards have become obsolete. How will this influence the mechanical movement production branch? There's no final answer to that, but it will undoubtedly have a lasting effect on the luxury watch landscape, and the future of haute horology will certainly be shaped in the light of Caliber 9RB2's achievement.

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However, end users do not need to worry, at least when it comes to Grand Seiko watches. Such a combination of ultimate engineering precision, groundbreaking achievements, and pushing the boundaries all over again, while also considering practical use and prolonged wear comfort, makes it possible for the Caliber 9RB2 to be made in such a small size. This speaks volumes about Grand Seiko's approach, with its engineering team and leadership constantly driven by the desire to develop groundbreaking innovations that align with its tradition, while always considering the end user.

After all, what good is any Caliber if it's not going to be a part of a watch that is regularly worn?

Written by S.K., images by Toni