As the Grand Seiko Evolution 9 continues to define the brand's exciting future, the venerable Japanese maker finally introduces its long-awaited mechanical chronograph, the Tentagraph. 

Just like every Grand Seiko creation, the pursuit of precision is at the heart of the new Tenta- graph, whose chronograph movement features the revolutionary high-beat Caliber 9SA5 as its base. Like Caliber 9SA5, the new Tentagraph Caliber 9SC5 beats ten times per second, ensuring high accuracy when measuring elapsed time as well as the time of day. And, thanks to its energy- efficient escapement and two barrels, the watch runs for three days even when the chronograph is in operation, making the Tentagraph the 10-beat chronograph with the longest power reserve in the industry today.* Furthermore, the Tentagraph is subjected to a new and longer testing procedure. As with all Grand Seiko mechanical movements, the Tentagraph’s time-of-day accuracy is assessed in six positions and at three temperatures over 17 days but, in addition, there are three more days of testing during which the accuracy is assessed in three positions while the chronograph is in operation. Thus, in total, each Tentagraph movement is tested for 20 days to ensure that it meets the Grand Seiko Standard of +5 to -3 seconds per day.

The new movement features the revolutionary Dual Impulse Escapement, which efficiently transfers energy to the free-sprung balance wheel indirectly through the pallet fork and also directly from the escape wheel. MEMS technology ensures extremely precise, lightweight, and highly durable escapement parts and also endows the escapement with increased energy efficiency to achieve a long power reserve. Hallmarks of a high-quality modern chronograph, a vertical clutch and a column wheel ensure high accuracy and operability. The vertical clutch eliminates any shuddering or jumping of the hands when the chronograph is engaged and enhances measurement accuracy, while the column wheel delivers precise control of the chronograph operation. The movement incorporates a three-pointed hammer, which ensures that, when the reset pusher is pressed, the hands return to zero instantly and in perfect synchronization.

The dial features Grand Seiko’s signature “Mt. Iwate pattern,” which takes inspiration from the ridged contours of the nearby mountain visible through the windows of the Grand Seiko Studio Shizukuishi, where the Tentagraph and all other Grand Seiko mechanical watches are hand-assembled and adjusted. The Mt. Iwate dial first appeared in 2006, and the pattern has since become deeply associated with Grand Seiko mechanical watchmaking. The majestic peak serves as an enduring inspiration for Grand Seiko, and its choice for the brand’s first mechanical chrono- graph is both symbolic and fitting. Combined with the gentle blue hue, the dial takes the imagina- tion upwards towards the night sky above Mt. Iwate.

Specifications

• Case Material : High-intensity titanium
• Glass Material : Box-shaped sapphire crystal with anti-reflective coating
• Lumi Brite : Lumibrite on hands, indexs and bezel
• Case size : Diameter 43mm × Thickness 15mm
• Clasp type : Three-fold clasp with push button release

Movement

• Caliber no. : 9SC5
• Movement Type : Automatic Hi-Beat
• Functions: Chronograph with 30-minute counter at 9 o’clock and 12-hour counter at 6 o’clock
• Power reserve : Approx. 72 hours(3 days)
• Accuracy : Accuracy (mean daily rate): +5 to -3 seconds per day

Functions

• Water resistance : 10 bar
• Magnetic resistance : Equipped
• Other details / Features :
• 60 jewels
• Screw-down crown
• Exhibition case back
• Serial number engraved on the case back
• Stop seconds hand function