Back in the 1830s, the bitter winter climate in the western Russian town of Vjatka (modern-day Kirov) prompted carpenter Semyon Ivanovitch to start producing pocket watches made entirely from wood — the reason being that the material is far less susceptible to thermal variations than metal and can therefore make for a mechanism that will remain accurate in extremely cold places.

But the cleverly-textured faux wood dial of this new Grand Seiko Tree Rings watch is there for purely aesthetic reasons — because underneath it beats a movement so accurate that it is said to lose or gain no more than half-a-second a day, regardless of the temperature in which it is operating.

Called the Caliber 9RA2, it is the latest interpretation of the hybrid Spring Drive system which mingles mechanical and quartz technologies. As the watch unwinds, a rotor produces the tiny amount of electricity required by a quartz crystal to relay a reference signal to the movement’s regulator, thus doing away with the need for a battery while still ensuring exceptional accuracy.

The Spring Drive system debuted in 2004, but only now has it been sufficiently refined and reduced to enable it to be used in models such as the Tree Rings, a slim dress watch with an impressive five-day power reserve.

To achieve such a level of autonomy in a thinner-cased, Spring Drive watch, the movement incorporates two barrels, one large and one small, and the power reserve indicator has been moved to the underside where it can be monitored through the sapphire crystal case back.

The impressive accuracy parameters are made possible, meanwhile, by a combination of a new integrated circuit containing a built-in temperature sensor and the use of handpicked quartz oscillators that have gone through a three-month ageing process to ensure they are ultra-stable.

Prior to assembly of the movement, the oscillator and sensor are vacuum-sealed into a single package to eliminate even the slightest temperature difference between the two, thus ensuring maximum accuracy.

The Caliber 9RA2 launches in the Tree Rings watch and another model, the steel-cased Minamo Lake Suwa, which recalls the lake near the Shinsu studio where Grand Seiko’s Spring Drive watches are created.

Grand Seiko Tree Rings
Grand Seiko Minamo Lake Suwa

Both commemorate Seiko’s 140th anniversary, with a rose gold Tree Rings being limited to 140 examples worldwide. It will be available in Grand Seiko boutiques from November, priced at about €50,000. The steel Minamo Lake Suwa will be made in an edition of 2021 watches, priced at £8,200 and going on sale a month later.

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