Power reserve: 72 h, 36000 variations / hours
Tentagraph is Grand Seiko’s first mechanical chronograph. The watch is powered by Caliber 9SC5, which features the revolutionary Caliber 9SA5 as its base. The new movement beats ten times per second, ensuring high accuracy when measuring elapsed time as well as the time of day. It has a power reserve of up to three days even when the chronograph is in operation, which, based on Grand Seiko’s research, makes the Tentagraph the 10-beat chronograph with the longest power reserve in the industry today.
The Tentagraph movement incorporates the Dual-Impulse Escapement, which efficiently transfers energy to the balance wheel both indirectly through the pallet fork and directly from the escape wheel. It also incorporates a vertical clutch and column wheel, ensuring high accuracy and operability, and a three-pointed hammer, which ensures the instant and synchronized return of the chronograph hands when the reset pusher is pressed.
As with all Grand Seiko mechanical movements, 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. 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.
In every way, Tentagraph represents the ideals of a Grand Seiko sports watch. The powerful hands and prominent indexes of the Evolution 9 Style ensure high legibility. The chronograph seconds hand and the minute hand are gently curved down towards the dial to enhance legibility. On the case, a Zaratsu-polished, distortion-free mirror finish and a delicate hairline finish alternate. The watch’s curved profile, wide lugs, and low center of gravity ensure comfort on the wrist.
The case and bracelet are made of high-intensity titanium, which is about 30% lighter and more scratch resistant than stainless steel to maximize durability. The bezel is made of ceramic to protect the watch from scratches and enhance durability. The two pushers ensure the operability required for measuring elapsed time at the highest level. The dial features Grand Seiko’s signature “Mt. Iwate pattern,” inspired by the mountain visible through the windows of the Grand Seiko Studio Shizukuishi, where the Tentagraph and other Grand Seiko mechanical watches are hand-assembled and adjusted.