Learn more about Caliber 9F
The Shinshu Watch Studio, home to horological innovation
The Shinshu Watch Studio, located within the Seiko Epson Shiojiri Factory in central Japan, is a fully integrated watch “manufacture” which is home to a team of dedicated designers, engineers and watchmaking craftsmen and women who, together, possess all the skills involved in the creation of some of the world’s very finest watches with its main focus being, of course, Grand Seiko. The origins of the studio go back more than seventy years when Daiwa Kogyo was founded to manufacture and assemble watch parts. It later merged with the Daini Seikosha Suwa factory to become Suwa Seikosha. This company created several now legendary mechanical masterpieces including Lord Marvel, Crown and the first Grand Seiko, as well as the world’s first quartz watch, the Quartz Astron. Today, the company is known as Seiko Epson and its watchmaking focus is on advanced technology watches, including its remarkable Spring Drive and Quartz 9F calibers.
A GMT function for the global village
The primary function of a GMT (Greenwich Mean Time) watch is to display simultaneously the wearer’s local time and the time in another time zone and it was created primarily for those who travel internationally. There are many ways to incorporate this feature, but in the case of Caliber 9F86, a 24-hour hand is added to the traditional three hand dial. So, for example, a traveler going from Japan to Hong Kong pulls out the crown to the first click and turns it anti-clockwise, moving the hour hand backward one hour. As a result, the 24-hour hand displays the time in Japan, and the hour hand shows the time in Hong Kong. Crucially, the seconds hand keeps moving throughout and the high accuracy rate of Caliber 9F86 is preserved.
The independent hour hand adjustment mechanism
The GMT function of Caliber 9F86 is displayed by the 24-hour hand and the preservation of the accuracy is made possible by the independent hour hand adjustment function. In normal use, the step motor moves all four hands but when the crown is pulled out to the first click and turned, the hour hand jumps forward or backward one hour. The wheel fitted on the hour hand axis to adjust time zones is moved by turning the crown. This is where the jumper—or more precisely, the hour jumper—plays its crucial role. The power of a spring is applied to make the hour hand move smoothly and accurately and it was in the creation of a jumper that would perform this function perfectly that the challenge to the Shinshu Watch Studio lay. Perhaps one day, Koike will divulge the secret of how it was achieved.