The company is rightly regarded as one of the world’s great makers of in-house watch movements, but it doesn’t make a mechanical chronograph. Grand Seiko makes chronographs, of course. But they live in the Spring Drive universe, rendering comparisons to the fully mechanical chronographs on the market imprecise.

Only a couple of years ago, Grand Seiko launched the next generation of its Hi-Beat mechanical calibers, which brought a level of technical, decorative, and finishing precision up to the standard of its already famous dials and ultra-high-end Spring Drive movements. While GS was developing the 9SA5, it was also working on a concept tourbillon with a remontoir constant-force mechanism. Now that mechanism has finally seen life in a sellable limited edition watch, the Kodo ref. SLGT003.

With the Kodo Constant-Force Tourbillon, launched with Grand Seiko’s arrival at Watches & Wonders Geneva, we have its first tourbillon, and first mechanical complication, for that matter (excluding its many GMTs). Seiko has, of course, made a tourbillon, but that watch, 2016’s Fugaku Tourbillon, was not a Grand Seiko but a Credor.

Considering that Grand Seiko has been around for 62 years and that this is the first time it has entered the arena of mechanical complications, the significance of the Kodo (Japanese for heartbeat) can’t be overstated. It symbolizes an evolution for the company, the opening of a new chapter in its history. This includes a complicated mechanical watchmaking studio in Tokyo’s Ginza district to rival the well-known Micro Artist Studio for Spring Drive – as well as, it appears, some of the more famous mechanical watchmaking ateliers in Europe. During Watches & Wonders, we spent time with this watch in the Grand Seiko booth and took the photographs you see here.

In 2020, Grand Seiko announced an uncased concept tourbillon movement, which it called the T0. Developed by Grand Seiko R&D engineer and watchmaker Takuma Kawauchiya and his team over five years, caliber T0 was a tourbillon paired to a remontoir constant-force mechanism. A remontoir is essentially an intermediate source of power between the mainspring and the escapement. Usually a spring attached to one of the train wheels, it takes power from the mainspring before giving it to the escapement in even increments, the principle being that while a mainspring loses power gradually and therefore provides less and less power to the escapement, a smaller spring can serve up power in consistent doses over a longer time.

You might have had this experience yourself with a conventional mechanical watch. As the mainspring winds down toward the end, it has the effect of making the watch run faster. This is because diminishing power results in a loss of amplitude in the balance. A remontoir prevents this from happening by not passing along too much or too little power early or late in a watch’s power reserve.

As long as there is enough energy in the mainspring to wind the remontoir, it will deliver a constant supply of power to the escapement. By combining both a remontoir and a tourbillon, Kawauchiya’s constant-force tourbillon accounts for both positional errors (the tourbillon) and variation in energy supply (the constant-force mechanism), two of the factors that affect chronometry in mechanical watches. While tourbillons have become ubiquitous across a wide spectrum of price points and brands, constant-force mechanisms remain a rare thing.

Jack Forster penned an In-Depth article explaining the technical achievement that was the T0 concept movement. But a concept it was. For one thing, it was large enough to preclude its inclusion in a cased-up, sellable watch. But all that has changed.  The Kodo’s movement has been modified and shrunk down to fit the wrists of collectors.

The close integration of the two complications allows for a seamless delivery of power, which results in favorable rate stability over the constant-force mechanism’s approximately 50 hours of performance, though the watch itself has 72 hours of reserve. This mechanism also heralds a new standard for testing at Grand Seiko. According to the brand, each movement is tested for a full 48 hours in each of six positions and at three temperatures. Each movement is evaluated for more than a month – 34 days, to be precise, and the chronometric performance of each watch is recorded on a certificate provided with the watch.

Taking a page out of traditional open tourbillon displays, this combined mechanism is also a sub-seconds display, but in the case of the Kodo, a ruby on the constant-force carriage acts as the second hand, making it a deadbeat seconds. In the image below, note the upper object with the three largest arms in the structure at six o’clock. This is the bridge over the tourbillon/constant-force mechanism. Below that is the constant force carriage, which has three arms, including the one with the ruby indicator. And below that is the tourbillon carriage, which also has three arms. While it can be difficult to discern the two carriages from one another in a static picture, it’s much easier when you see the constant-force carriage jumping in one-second increments juxtaposed with the smooth turning of the tourbillon carriage below.

As it is a skeleton watch – Grand Seiko’s first – the dial of the Kodo is, in effect, its movement. And while this could have been a disadvantage, say, when comparing the Kodo to other masterpieces by Grand Seiko, the construction of the movement and essential parts of the interface more than make up for the lack of some finely textured dial or stark white enamel canvas. Light penetrates the watch from various angles and enhances the interplay of bright and dark. As I zoom in on the hands and indexes in Atom Moore’s photographs, I find that these components show no imperfections.

On the wrist, the Kodo plays with light and shadow in a beguiling way thanks to its open construction and, again, the finishing of those hands and markers. Notice the additional downward sloping facet on the hour hand as it nears the tip. Nobody would have thought to criticize this hand if it weren’t there, and yet there it is, providing another point for light to reflect. Throughout the movement, we see six-slotted screws.

On the wrist, the Kodo is, as I expected, a formidable presence. Its 43.8mm diameter and 12.9mm thickness ensure that you cannot forget you have it on. But it’s not big for this kind of watch really, and even if it were smaller and more slender, this isn’t the kind of watch capable of receding into the background. From the side, you can see that the case has a gentle curve to it, with wrist-hugging lugs and a box crystal that provides a significant portion of the finished watch’s height. We also see that the six-slotted screw style found throughout the movement has also been used to attach the strap at the lugs. Conventional screws on the back secure the see-through caseback.

The Kodo’s case is made from a combination of 950 platinum and Brilliant Hard Titanium, and Grand Seiko’s signature Zaratsu-polishing enhances the light reflection on the case. There is an inner case and bezel in platinum 950 and the exterior case sides and bezel are made from Brilliant Hard Titanium. It’s as brilliant as platinum and twice as hard as stainless steel.

At first glance in press images, I thought this was a galuchat, or stingray, strap. But that’s not the case. It’s a calfskin strap treated with real Japanese Urushi lacquer made with sap harvested from Japanese trees. The material is commonly associated with Japanese artworks and tableware, but here the stunning black look and texture provide additional depth to the Kodo watch. The strap is water-resistant, a quality you might not expect, but consider that the lacquer on it is used to make objects that routinely get wet, such as fine chopsticks and miso soup bowls.

The Kodo tourbillon SLGT003 truly is a masterpiece, as Grand Seiko classifies it. And its appearance at Grand Seiko’s very first Watches & Wonder’s Geneva delivered a feeling of evolution for the brand.

The halls of the Geneva Palexpo have ushered some very monumental pieces of high-watchmaking into the public consciousness, from brands with names like A. Lange & Söhne, Vacheron Constantin, and Audemars Piguet. Several of the most important brands in the watch industry joined Watches & Wonders for its first physical Geneva show. With no shortage of noteworthy watches, it’s worth considering that the most talked-about high-complication of 2022, so far, came from Grand Seiko.

The Grand Seiko Kodo Constant-Force Tourbillon Ref. SLGT003 features the manually wound Caliber 9STI beating at 28,800 vph and running in 44 jewels for a power reserve of 72 hours (50 hours of constant force with accuracy of +5 to -3 seconds per day). It is water-resistant to 100 meters and comes in a 43.8mm x 12.9mm Zaratsu-polished case made of 950 platinum and Brilliant Hard Titanium. The retail price is $350,000 and there will be 20 pieces made. 

All photos by Atom Moore