Tentagraph Caliber 9SC5 To fully showcase the capabilities of this new mechanical chronograph movement, Grand Seiko has also introduced a new standard specific to mechanical chronographs that requires a mean daily rate of -3 to +5 seconds per day, testing across 17 days, three temperatures, and six positions without the chronograph in use. However, in addition, this new GS Standard will include three additional days of position testing with the chronograph in use, creating testing criteria of 20 days. The addition of the chronograph running in the test is not applied to chronographs submitted using COSC or ISO chronometer standards. It pushes to enforce the quality of the movement further while the chronograph is in use. For the chronograph module, functionality is critical. The use of a column wheel is implemented to provide a reliable, error-free operation that provides a noticeable “click” when the pushers are depressed. Along with the column wheel, a vertical clutch provides a shudder-free operation of the second hand when starting the elapsed time measurement. By dropping the clutch to engage with the driving seconds vertically, as opposed to horizontally meshing gears together, the engagement is smooth and precise, eliminating the possibility of teeth slipping due to their lateral engagement and misalignment of the teeth when interacting. This may cause the gear to shift backward, in turn making the second hand shudder. The vertical clutch eliminates this imprecision. The use of the vertical clutch and column wheel mechanism has deep roots within both former Seikosha factories in the late 1960s and through the 1970s. In 1969 Suwa Seikosha (Now Seiko Epson) introduced the 6139 calibers as the world’s first automatic chronograph incorporating a vertical clutch and column wheel system. The following year, Daini Seikosha (now Seiko Watch Corporation) introduced the caliber 7016, including the vertical clutch and column wheel system but in a thinner profile. Over the decades, both Seiko and later Grand Seiko have continued the pursuit of high-grade chronographs utilizing this system, and the knowledge and know-how of past developments have proven the value and performance of this method of measuring elapsed time. The introduction of the Tentagraph Caliber 9SC5 required an impressive aesthetic. Grand Seiko Style, its unique design grammar, was established in 1967 in the introduction of the 44GS. This design code was evolved for the modern day by Grand Seiko designer Kiyotaka Sakai in 2020. This newly established design code was later introduced as the Evolution 9 Collection, and at Watches and Wonders 2022, sport model iterations were added to the lineup. For the Tentagraph, a new take on the Evolution 9 was conceived and harmonized with the new movement. The Evolution 9 aesthetic is similar to that of the original Grand Seiko Style; however, a focus on improved legibility through wider and grooved, highly faceted indexes and distinct shapes for the hour and minute hands creates incredible legibility and a bold dial. The Tentagraph adds Lumibrite, a proprietary luminous paint, to the indexes and hour and minute hands. The case shape involves many intersecting planes, alternating mirror-finished surfaces with a soft hairline finish, with sharp edges formed by the acclaimed Zaratsu polishing technique. The bezel is made of zirconia ceramic for high durability and scratch resistance and adds a tachymeter, an uncommon trait on a Grand Seiko bezel. Comfort is the emphasis for Evolution 9. The wide and thick bracelet and a case with a low center of gravity help create a sense of balance on the wrist. The use of high-intensity titanium alloy gives a lightweight feel but creates high scratch and corrosion resistance for long-term usability. The clasp also features micro-adjustments but is not oversized compared to the bracelet. The pushers stand out compared to some of the Spring Drive Chronograph GMTs, as the Tentagraph has a low profile yet is still highly functional. They are in line with the crown, despite the modular structure. The multi-layered dial improves legibility with recessed sub-dials for the chronograph hour and minute counters and continuous running seconds. The stunning texture expresses the ridges of Mt. Iwate, as seen from above, radiating out of the dial’s center. This dial pattern was first implemented in Grand Seiko in 2006 and is exclusively used alongside the 9S series of calibers, which are made at Grand Seiko Studio Shizukuishi in Iwate Prefecture, Japan. A symbol of Iwate, the mountain has also become synonymous with Grand Seiko mechanical watches. The studio that crafts these timepieces often pays tribute to the peak, as seen from their windows. The medium shade of blue pays homage to the night sky over Mt. Iwate, and its subtlety and charm only further enhance this amazing new addition to the lineup.