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Grand Seiko Kodo Constant-force Tourbillon won the Chronometry Prize for its high-precision timekeeping performance

Audrey Simon
Audrey Simon • 4 min read
Grand Seiko Kodo Constant-force Tourbillon won the Chronometry Prize for its high-precision timekeeping performance
Grand Seiko Kodo Constant-force Tourbillon won the Chronometry Prize for its high-precision timekeeping performance
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Grand Seiko has secured its position in the world of horology with a prestigious award, the Grand Prix d’Horlogerie de Genève, which is the industry’s equivalent of the Oscars. The Japanese brand competed with 15 other timepieces and was awarded the winner by a jury of 30 who selected the Grand Seiko Kodo Constant-force Tourbillon as the winning watch for the Chronometry Prize.

The award was accepted by Akio Naito (right), president of Seiko Watch Corporation, and Grand Seiko’s movement designer Takuma Kawauchiya, (left), who designed and assembled the winning watch.

This comes as no surprise as Grand Seiko has been steadily growing in strength over the years. says:, “While the Swiss watch industry is recognizsed for its centuries-long striving for this perfection, leave it to the Japanese to bring that level of perfection up to standards that are unmatched. One of the best examples of this desire to create the best wristwatches in the world lies with Grand Seiko”.

Founded in 1960, Grand Seiko, was part of the Seiko Watch Company until the split in 2017. Grand Seiko is now fully independent and has come into its own and has taken the luxury watch industry by storm.

And the winner is…
To understand the Grand Seiko Kodo Constant-force Tourbillon is to look back to 2020, when the timepiece was a concept movement with a constant-force mechanism and a tourbillon as one unit on a single axis.

From here, a dedicated team diligently worked on the concept to bring it to reality. Designers, engineers, and craftsmen and craftswomen worked on the 340 components of the caliber and the end-result is Caliber 9ST1, which was reduced in size from the original. Smaller does not mean accuracy is sacrificed., On the contrary, it remains stable for longer thanks to the constant-force mechanism.

In addition to that, the Caliber 9ST1 sets a new standard of accuracy, which is verified in a testing procedure during which each movement is tested for a full 48 hours in six positions and at three temperatures, twice as long as the Grand Seiko standard. Each movement is assessed over the course of 34 days to verify its accuracy, and 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.

The watch is named Kodo, or “‘heartbeat’” in Japanese, after the unique motion of the two mechanisms and the sound of the rhythm it makes. The inner tourbillon carriage rotates smoothly as the balance steadily vibrates at eight 8-beats per second, and the outer constant-force carriage follows its rotation at one-second intervals to create a 16th-note rhythmic feel.

The components are finished by hand using a variety of techniques, to give the movement its shine, a hallmark of Grand Seiko. The case is constructed of both Platinum 950 and Grand Seiko’s Brilliant Hard Titanium to achieve long-lasting beauty.

See also: Musée Atelier Audemars Piguet takes visitors on a journey through the cultural legacy of the Swiss manufacturer

Tech specs
Case back

See-through case back with six6 screws


Movement Type
Manual winding

Power reserve
Approximately. 72 hours (3three days). (Constant-force: 50 Hhours)

Mean daily rate
+5 to -3 seconds per day
Mean daily rate is a mean value of daily rates in a condition where the movement before assembly in a case is measured in six positions in a fixed manner. This is done under an artificially controlled environment for 12 days.

Water resistance
10 bar

Magnetic resistance
4,800 A/m

132 g

Other details
Serial number is engraved on the case back
Platinum 950 clasp (partly 18k white gold)
Power reserve indicator

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