Why American journalists call Grand Seiko a "giant": The huge impact the T0 and 9SA5 had on the industry

For the past 60 years, Grand Seiko has pursued the creation of some of the world's most accurate timepieces through the development of quartz, mechanical, and Spring Drive watch movements. Now, with the release of the T0 Constant-Force Tourbillon, the Japanese giant has truly entered the world of haute horlogerie.

The T0 Constant-Force Tourbillon, the epitome of Grand Seiko technology

　In September 2020, Seiko Watch unveiled the "T0 Constant-Force Tourbillon" (commonly known as T0) as a Grand Seiko concept creation. It is the world's first movement to feature a tourbillon on a coaxial axis while fully integrating a constant-force mechanism.

　The goal was to give mechanical watches the highest level of precision and prestige. The constant-force mechanism ensures a stable supply of energy to the escapement regardless of the winding status of the mainspring, and the tourbillon eliminates errors caused by gravity by enclosing the escapement parts and balance wheel within the rotating carriage.

　The T0 is not Seiko's first tourbillon model. In 16, Credor released the "Fugaku Tourbillon Engraving Limited Edition." It's also not the first watch to combine a remontoire and a tourbillon. However, it is certainly a first for Grand Seiko, and the company has announced that it is the world's first watch to combine a remontoire and a tourbillon on a perfect axis.

　While most movements with a constant-force mechanism are separated from the carriage, the T0 uses a gear located coaxially with the carriage to store torque, and the energy gained as the mainspring unwinds is used to power the rotating carriage and balance.

　According to Seiko Watch movement designer and watchmaker Takuma Kawauchiya and his team, the T0's performance in the lab, with a power reserve of over 50 hours, is a testament to its design. In fact, the T0 achieved an incredible accuracy of ±0.5 seconds per day.

　Kawauchiya tried an unconventional approach when manufacturing the T0 gears. To achieve greater precision than traditional machining, he chose a manufacturing process called MEMS (Micro Electro Mechanical Systems), which is used in semiconductor manufacturing.

　This technique involves layering metal films in a plating-like fashion, allowing for precise tooth shapes to be achieved down to the micron level. The same process was already being used to make Grand Seiko pallets and balance wheels, but this is the first time that this technique has been applied to almost all gears.

　A ceramic gear was chosen for the stop wheel for its durability and reduced friction.Another feature of the movement is that while the tourbillon carriage (made of blued titanium) rotates, the outer carriage is stopped by a stopper and stop wheel, resulting in a deadbeat for the seconds hand.

　The T0 was developed over a period of more than five years, with the hand-finishing alone taking three months. The new movement has two parallel barrels, providing a power reserve of approximately 50 hours.

　The T0 is 36mm in diameter, 8.22mm thick (including the tourbillon), and is made up of 340 parts. Surprisingly, the movement is based on Grand Seiko's Cal. 9S65, "the most standard automatic movement in the 9S mechanical series."

　The balance wheel therefore vibrates at 28,800 vibrations per hour, which is standard for modern mechanical watches, but this time it also includes a remontoire and tourbillon. Still in the concept stage, the T0 is not a mass-produced model.

　However, since 2021 marks the 220th anniversary of the birth of the tourbillon (Abraham-Louis Breguet patented it on June 26, 1801), we expect Grand Seiko, which has always been committed to the precision of its mechanisms, to create a "tourbillon" (a whirlwind) of innovations aimed at improving precision.

Cal. 9S65, the basis for the T0

　The Caliber 9S65, which is the basis for the T0, is also featured in the most recent limited edition Grand Seiko 60th anniversary watch, the Grand Seiko Ref. SBGR321. This announcement follows the opening of the Grand Seiko Studio Shizukuishi in July 2020.

　Grand Seiko Studio Shizukuishi is home to Morioka Seiko Kogyo's Shizukuishi High-End Watch Workshop, a luxury watch and movement production base in Iwate Prefecture "specializing in the production of Grand Seiko mechanical watches and other high-end timepieces."

　The deep blue dial is said to be inspired by "the sparkling blue sky that spreads over the mountains of Iwate and the dawn that greets the watchmakers and technicians at Grand Seiko Studio Shizukuishi."

　The 40mm stainless steel case is fitted with a matching three-fold push-button steel link bracelet, and is water resistant to 100m and antimagnetic to 4800A/m. The movement, visible through the sapphire crystal case back, has been manually adjusted and inspected at Grand Seiko Studio Shizukuishi. Accuracy is adjusted to within +5 to -3 seconds per day, the movement beats at 28,800 vibrations per hour, and the power reserve is approximately 72 hours. The Ref. SBGR321 is limited to a production run of 2500 pieces, priced at 550,000 yen.