No Longer a Concept: Grand Seiko’s Constant-Force Tourbillon Movement Goes into Production with the All New Kodo

It’s not entirely shocking that Grand Seiko has taken their T0 concept tourbillon movement announced back in 2020 and put it into production for a new and completely bonkers highly complicated limited edition, but I don’t know that anyone really expected this watch to turn up so soon, less than two years since the experimental movement was unveiled. This week at Watches & Wonders, Grand Seiko has done just that, announcing the Kodo Constant-Force Tourbillon. The watch sets a new high watermark for Grand Seiko in terms of complicated watchmaking, pushing them into haute horlogerie territory occupied mainly by a slew of Swiss brands and independent watchmakers that one doesn’t normally think of occupying the same space as Grand Seiko. That only speaks, however, to the incredibly rapid growth of the brand, and their impressive ability to play at seemingly any level they choose, from quartz sports watches coming in at around $3,000, to the Kodo seen here, which – trust me – is considerably more expensive.


It would be a mistake to assume that the Kodo simply runs a version of the T0 caliber scaled up to meet a small production run, and Grand Seiko has given this movement a new name to drive that point home. The 9ST1 caliber is the product of many small refinements to the T0, which was essentially rethought component by component to create a movement that would be suitable in a wristwatch that Grand Seiko could actually sell. The 9ST1 is notably smaller than the T0, and Grand Seiko has put it through a battery of tests to ensure accuracy. Specifically, movements are tested for 48 hours in six positions and three temperatures, and evaluated for a total of 34 days thereafter. Once a 9ST1 movement meets or exceeds Grand Seiko’s expectations for precision, its performance characteristics are detailed on a certificate supplied with each Kodo. 

In terms of its technical merits, what the movement actually does, there’s still plenty of overlap with the T0. This is not just any constant-force tourbillon (as if such a movement could ever be run of the mill), but distinguishes itself by integrating the constant force carriage and tourbillon cage into a single unit working on a common axis. In developing the new movement, Grand Seiko discovered a number of benefits to this design, including an increased power reserve and a more stable amplitude on the watch’s balance wheel. This is a direct result of the fact that there are no bridges or wheels between the constant-force mechanism and the tourbillon, and that consistency in timekeeping across a watch’s entire power reserve is the goal behind implementing a constant-force system in the first place. 

The visual impression of the movement in action is unlike any other watch. The tourbillon carriage (which sits inside the constant force mechanism) rotates in the manner you’d expect from a tourbillon. What makes this movement special though is the way that the constant force system follows the path of the tourbillon at precise one second intervals, effectively making the Kodo a deadbeat seconds watch as well. It’s also worth pointing out that the movement has a specific and finely tuned sound, combining the once-per-second “click” of the constant force mechanism with the familiar beat of the high frequency escapement. It’s hard to describe in words, but there’s a musical quality to it that’s really appealing, and it wasn’t a surprise to learn that the movement’s chief designer has a background in music. 

The Kodo’s case is intricate in the much the same way as the movement, mirroring it in the sense that there’s an inner and outer section that work together to form a balanced design. The inner case is platinum, and the outer case is Grand Seiko’s Brilliant Hard titanium – you can see where they meet at the tips of the lugs, where you’ll find a small open space. Grand Seiko has finished the case with both Zaratsu polishing and precise brushing. The case shape creates a clear link to Grand Seiko’s current line of Evolution 9 watches, which is the brand’s next generation design language and the current home of their latest and greatest Hi-Beat and Spring Drive calibers. It’s worth remembering that the T0, and thus the new 9ST1, has its roots in the development of the 9SA5 high frequency caliber. When you step back and look at the Evolution 9 family, it’s remarkably cohesive.

It’s hard to overstate the importance of the Kodo’s launch to Grand Seiko. Not only is it a massive technical achievement, but it cuts a new path into a different type of artistic watchmaking than what we’re used to seeing with Grand Seiko. This watch isn’t inspired by the seasons or nature, but according to the brand is a reflection of Ginza nightlife, and the creation of the Kodo marks the beginning of an entirely new Grand Seiko studio, Atelier Ginza, which exists to create the most unique watches in the Grand Seiko lineup. Ginza is where Seiko began in 1881, so there’s a strong connection between the brand and the city, and it’s exciting to think about what types of watches we’ll see come out of this new studio in the future. Mostly, though, it’s just impressive to see Grand Seiko flex like this, showing all that they’re capable of at the moment in creating something both artistically daring and so impressive and unique from a purely horological standpoint.

The new Grand Seiko Kodo is priced at what can only be described as an eye watering $350,000. A total of 20 will be made, with delivery expected in September. Grand Seiko

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Zach is a native of New Hampshire, and he has been interested in watches since the age of 13, when he walked into Macy’s and bought a gaudy, quartz, two-tone Citizen chronograph with his hard earned Bar Mitzvah money. It was lost in a move years ago, but he continues to hunt for a similar piece on eBay. Zach loves a wide variety of watches, but leans toward classic designs and proportions that have stood the test of time. He is currently obsessed with Grand Seiko.