Grand Seiko "The Ultimate Quartz GMT"
The 9F Quartz movement is Grand Seiko's signature masterpiece. In addition to its ultra-high precision of ±10 seconds per year, it has a powerful torque comparable to that of a mechanical movement, and is theoretically durable enough to last for approximately 50 years without running out of oil, making it one of the finest standalone movements. 2018 marked the 25th anniversary of the 9F Quartz movement, and a new GMT function was added. This amazing feature is worthy of the 9F Quartz masterpiece.
Interview and text by Masayuki Hirota (Chronos-Japan)
Caliber 9F 25th Anniversary Limited Edition Model SBGN001
This is the first GMT model to join the 9F Quartz movement. While the regular model has a lacquer-finished dial, this limited edition features a 9F 25th anniversary limited edition die-stamped dial with a "GS" and "9F" pattern. Noteworthy is the fact that "9F25" is engraved in only one place. The dial color is charcoal gray. The limited edition model's annual accuracy has also been improved from the usual ±10 seconds to ±5 seconds. Quartz movement (Cal. 9F86). Stainless steel (diameter 39.0mm, thickness 12.1mm). Water resistant to 10 bar. Exclusive to Grand Seiko Master Shops. Limited to 800 pieces worldwide. Price: 370,000 yen. Scheduled for release on October 12th.
9F Quartz Movement: 25 Years of Renewal and Evolution
Quartz movements are highly accurate, but the torque required to move the hands is not great. As a result, the only way to add functions was to increase the number of motors that move the hands. The only exception to this was the Grand Seiko 9F Quartz, which was first released in 1993. In 2018, marking its 25th anniversary, its immense torque, comparable to that of a mechanical movement, allowed for the addition of independent correction functions for the GMT and hour hands, as well as the ability to advance and reverse the date in tandem with these, and even an instantaneous date advance function.
(Left) SBGN003 / (Right) SBGN005
This is the regular 9F Quartz GMT model. The ability to independently adjust the hour hand makes it even easier to use. The two-tone finish on the faceplate, which makes it easier to distinguish between day and night, is a vibrantly colored print rather than painted. The crown has also been changed to a highly water-resistant screw-down type. The precise feel when turning the crown lives up to the 9F name. Accuracy: ±10 seconds per year. Quartz movement (Cal. 9F86). Stainless steel (diameter 39.0mm, thickness 12.1mm). Water resistant to 10 bar. Exclusive to Grand Seiko Master Shops. Price: 330,000 yen. Scheduled for release in January 2019.
The 9F GMT model, released in 2018, features a second time zone display using the GMT hand, independent hour hand adjustment, and the ability to advance and reverse the date in conjunction with independent hour hand adjustment. These are functions that are difficult to incorporate into a quartz movement, but the 9F's immense torque makes them possible. Additionally, this model retains the instantaneous date advance function, a hallmark of the 9F. While this may seem obvious, there are very few movements with the ability to advance and reverse the date in conjunction with independent hour hand adjustment that also feature instantaneous date advance. While this makes it even easier to use, it is quite difficult to achieve the coexistence of these functions.
The person who added the GMT function to the 9F Quartz watch was Nobuhiro Koike, who works in Seiko Epson's Wearable Devices Division. He has been involved in the development of the 9F since its inception and is a walking encyclopedia, so to speak. "The plan to add the GMT function and independent hour hand correction function to the 9F was there from the time the 9F was first announced. It would be a shame to stop the watch every time the time difference needs to be corrected, even though we have achieved high accuracy of ±10 seconds per year. If the instantaneous date advance function were not available, it would be easy to add these functions. However, we did not want to add independent hour hand correction function at the expense of the instantaneous date advance function, which is a distinctive feature of the 9F."
To move the date forward or backward in conjunction with the hour hand independent correction function, all you need to do is attach a protrusion to the date indicator wheel, which is connected to the hour wheel and rotates once a day, and then hook the date display onto it and turn it. The design is not particularly difficult. On the other hand, instantaneous date advancement accumulates torque in a spring through the rotation of the hour wheel, and the force of releasing this torque moves the date display instantly. The instantaneous date advancement, which charges the spring over time, and the hour hand independent correction function, which hooks onto the protrusion on the date indicator wheel and gradually moves the date forward or backward in a short time, are different designs, and it is quite difficult to achieve both.
