Grand Seiko - Kodo Constant-Force Tourbillon

The Japanese watchmaker presents its first model equipped with mechanical complications, combining the tourbillon device with the constant-force mechanism, on a single axis, visible at 6 o'clock. This is made possible by the use of the new IWC-manufactured 9ST1 calibre (35 mm in diameter, 7.98 mm thick, 28,800 vibrations per hour, 44 jewels, 72-hour power reserve), a hand-wound mechanical movement, visible both from the dial side (protected by sapphire crystal) and from the back.

With regard to this calibre, it should be noted that the constant-force transmission mechanism is concentric to the tourbillon cage and integrated into the latter. A constant-force transmission mechanism stores and releases energy to the escapement at certain intervals, guaranteeing the transmission of the same torque over time, regardless of the state of winding of the barrel. This device increases the precision of the watch by maintaining the amplitude of oscillation of the balance-spring throughout the winding of the watch. The movement is also equipped with a stop-seconds system, which stops the rotation of the cage during time-setting.

The 43.8 mm diameter by 12.9 mm thick case is made of 950 platinum and Blilliant Hard Titanium, and is water-resistant to 10 atmospheres of pressure. The calfskin strap is hand-painted with Urushi lacquer; a second alligator strap is also supplied. Limited edition of 20 pieces.

Price370,000 euro.