A Unique Heartbeat: The Piece-Unique Grand Seiko Kodo Constant-Force Tourbillon SLGT001

Grand Seiko reached a new milestone in its sixty-two-year history with the introduction of the brand’s first mechanical complication watch, the Grand Seiko Kodo Constant-force Tourbillon. At its heart is a uniquely innovative movement that delivers a level of stable accuracy unprecedented for Grand Seiko by combining a tourbillon and a constant-force mechanism as one unit on a single axis for the very first time in horological history. The watch is named Kodo, the Japanese word for heartbeat. With its unique appearance when in motion and with its carefully designed sound, this revolutionary watch reveals its vitality both audibly and visually, thanks to the open-work design and the sapphire case back. Most remarkable of all is the way that the constant-force mechanism and the tourbillon have been integrated together to allow the creation of an overall design that is perfectly in harmony with the values of Grand Seiko and whose technical ingenuity is encased in a watch of great elegance and wearability.

In 2020, Grand Seiko introduced the “T0 Constant-force Tourbillon”, a concept movement incorporating a constant-force mechanism and a tourbillon as one unit on a single axis. To bring the concept to life in a finished watch required the complete dedication of a team comprising designers, engineers, and craftsmen and women entrusted with the assembly and finishing of the movement and the case. Each of the 340 components of the caliber was re-examined and, where necessary, re-designed and re-engineered for production. The result is Caliber 9ST1. Not only is Caliber 9ST1 smaller than its concept movement predecessor, but its high accuracy remains stable for longer thanks to the constant-force mechanism. Furthermore, Caliber 9ST1 sets a new standard of accuracy, verified in a testing procedure during which each movement is tested for a full 48 hours in each of six positions and at three temperatures. This is twice as long as the Grand Seiko Standard. Each movement is assessed over 34 days to verify its accuracy. When the tests are completed and this new standard has been met or exceeded, the performance characteristics of each movement are defined in the individual certificate provided with every watch.

For the Kodo model unique piece to be sold exclusively by Phillips Auction, SLGT001, the concept was based on musō 無双. Musō roughly translates to “one and only” or “second to none,” a fitting term for the unique piece exclusive to the auction. This unparalleled model is unique in several ways compared to the global model limited to 20 pieces, reference SLGT003.

First, the multi-component case structure is made entirely of Grand Seiko’s proprietary alloy, Brilliant Hard Titanium. This material, which is used on only the outer case and outer construction of the bezel of SLGT003, is used for both the inner and exterior case components to thoroughly reduce weight and achieve a comfortable feel unique to this model. Brilliant Hard Titanium is as light as pure titanium but twice as hard as stainless steel and, therefore, highly resistant to scratches. Its color is brighter than the other forms of titanium used for Grand Seiko, allowing the Zaratsu polished surfaces to stand out more prominently.

The bridges, mainplate, and many of the components of the movement are plated in a silver color to create an entirely new aesthetic for the Kodo. A yellow-gold accent for the power reserve and seconds track of the carriage inherits the aesthetic of the T0 concept movement.

The design of the screws for the Kodo model has the appearance of the six arms of the carriages, a trait that cleverly enhances the design but also is pleasant for assembly. The special screwdriver and screws used have an even application of torque, which the designer of T0 and Kodo, Mr. Takuma Kawauchiya, enjoys greatly. For the unique piece SLGT001, the screws are tempered blue by hand instead of being mirror polished as they are on reference SLGT003. 

The carriages for the constant-force tourbillon mechanism are titanium to help reduce weight and improve efficiency. They are blue as well, which is executed through anodic oxidation. Anodic Oxidation is a surface treatment in which the titanium carriages are subjected to electrolysis to generate an oxide film artificially. Titanium oxide film produces color according to the light refraction index, enabling the production of different colors by varying the thickness of the oxide film. This once again emulates the styling of the original concept T0.

The GS letters are specially engraved by hand on the Brilliant Hard Titanium clasp by Grand Seiko’s very best engravers. The watch is offered with a calf strap specially treated in the same traditional way as was used to create the high-durability material once used in the armor of the Samurai. The strap’s surface is painted by hand with Urushi lacquer in a multi-coating process that gives the strap a delicate sheen. It is in a brown color specially for this unique piece.  

Accompanying the unique piece Kodo SLGT001, will be an exclusive trip to Japan to meet its creators, the Grand Seiko team, a visit to Grand Seiko Studio Shizukuishi in the lovely Iwate prefecture.

A portion of the sale will be donated to the Children’s Heart Foundation. The Children’s Heart Foundation is the leading organization dedicated to funding congenital heart defect research.