It seems the Seiko and Grand Seiko brands are extra busy these days as they come out with a slew of compelling releases. There’s good reason aside from the usual motivation: It’s been 140 years since Kintaro Hattori founded the company that basically put an end to the Swiss chokehold on fine horology.

For Grand Seiko, there’s no better way to celebrate the feat than to release a new heart to drive its timepieces. The Spring Drive 5 Days Caliber 9RA2 closely follows the 9RA5 movement that GS unveiled last year to commemorate its own 60th birthday.

Slimmer and more compact than any Spring Drive heart, the new movement is touted by GS as bearing “understated charm and beauty.” Not many can lay claim to even seriously consider the aesthetics of a caliber that largely remains out of sight of the wearer, but GS doubles down on this. Through a sapphire caseback, the 9RA2 shines with what the brand calls a Shimsu Frost Finish. Even the movement mirrors the marque’s affinity with natural elements – specifically Japanese sights. “The delicate texture of the movement’s finish reflects the frost that winter brings to the forests in Shinshu where all Spring Drive watches are made. The bridge lines and hole edges are diamond-cut to reflect light from all angles and the jewels and tempered blue power reserve indicator add a quiet sparkle that is a delight to behold,” the company said.

The new caliber powers two new releases that demonstrate the brand’s abiding love and respect for nature. The blue-dialed SLGA007 is meant to, according to GS, “evoke the gentle sway of the water surface of Lake Suwa, with ripples and shallow waves that create a pleasing sparkle at whichever angle the dial catches the light.” This Grand Seiko Heritage Collection timepiece has a limited run of 2,021 examples. Even rarer with 140 examples is the SLGA008, whose dial is made to mimic dynamic wood grain. This is encased in an 18K rose gold case for added warmth and luxury.

Immediately obvious to Spring Drive observers is that the new movement grafts the power reserve indicator onto the back. Regardless of how you feel about this meter in the first place, the move undeniably frees up real estate so you get a better appreciation of what the takumi are trying to convey with the exquisite dials.

Aside from the GS branding and the aforementioned power reserve indicator on its backside, owners of 9RA2-equipped timepieces will see colored jewels and screws, and a legible “5DAYS” announcing the total reserve power (120 hours) past the oscillating weight. This long, worry-free period is made possible in part through two different-sized barrels.

The company says the changes are not all for show, either.

Aside from shaving the weight and compressing the new caliber, GS features a new execution of the Offset Magic Lever that, while allowing a reduction in the movement’s depth, also gives it the “same high winding efficiency.” Moving the lever away from the 9RA2’s center allows the thinner rendering. The hands are also set closer together, making the profile even more compact.

A one-piece center bridge which called for even more skillful hands holds everything together. Despite being smaller in heft, GS says that the new movement promises better rigidity and shock resistance.

The benefits extend to the dial and date window as well. From an angle, where most of us, says GS, checks out the time, legibility has been improved owing to the more compact assembly – particularly of the hands. The shallower date window means its sides will not cast a shadow on the date.

Spring Drive has long stood for accuracy, and this newest in the Seiko line does not disappoint. It keeps a reliable cadence that yields only ±10 seconds per month. Grand Seiko explains that this is made possible by “a new IC with a built-in temperature sensor, and to the selection of highly stable quartz oscillators that have gone through a three-month aging process. The quartz oscillator and temperature sensor are vacuum-sealed into a single package to eliminate even the slightest temperature difference between the two to maintain the watch’s accuracy at the highest possible level.”

Versus the 17-year-old 9R65, the 9RA2 is 14 percent thinner and 25 percent more compact. This movement is also quieter, and promises better comfort through a lower center of gravity. GS adds that its wind torque is almost the same, while the quality of sound has been upgraded.

We have yet to see if this much-improved movement will make it beyond the limited edition runs of Grand Seiko. That would be, well, another grand move.