Grand Seiko’s New Spring Drive Caliber Debuts in a Serious Professional Diver, the SLGA001

The 60th anniversary of Grand Seiko has proven to be a time of real inspiration for the brand, releasing a series of celebratory models that amount to real horological advances, dutiful nods to the past, and a taste at what the future might hold in terms of the brand’s overall design aesthetic. We previously covered new releases that highlighted Grand Seiko’s excellent quartz calibers, and just showed you a breathtaking advancement in the realm of their high frequency movements, involving the invention of an entirely new escapement. Now, we turn our attention to Spring Drive, perhaps the movement technology most closely associated with the brand. To debut their new 9RA5 caliber, representing the next generation of Spring Drive tech, Grand Seiko has introduced a professional diver that takes full advantage of the caliber’s accuracy, reliability, and extended power reserve.

Grand Seiko SLGA001

  • Case Material: Titanium
  • Dial: “Grand Seiko Blue”
  • Dimensions: 46.9 x 16mm
  • Crystal: Sapphire     
  • Water Resistance: 600 meters
  • Crown: Screw down               
  • Movement: 9RA5
  • Strap/bracelet: Titanium bracelet
  • Price: $11,100 
  • Reference Number: SLGA001
  • Expected Release: August 


Spring Drive, as most longtime readers of this site will be aware, is a technology that combines the accuracy of quartz timekeeping with a traditional mechanical gear train. Spring Drive watches are powered by a mainspring, never require a battery, and are capable of astounding accuracy. All that, and they provide one of the most satisfying visual parlor tricks in all of horology, with the smooth, completely uninterrupted sweep of the seconds hand across the dial. Spring Drive watches have been favorites of enthusiasts since they debuted in 1999, and have gradually gained more mainstream acceptance in the watch community over the course of the last twenty years.

The new 9RA5 caliber is a significant advancement. It’s thinner, more accurate than its predecessor, and has a longer power reserve. That extended power reserve is really the key advancement, at least as it pertains to the SLGA001, the professional diver in which the new caliber makes it debut. Grand Seiko is able to achieve a total power reserve of 5 days through the use of two mainspring barrels, one significantly larger than the other. The sizing of the barrels allows Grand Seiko not only to make the most of the limited space they have to work with in designing the movement, but enables the correct amount of torque to be delivered throughout the entire power reserve, ensuring even power consumption for all five days that the watch may run without being wound. In other words, you could conceivably wear the watch for a day, leave it for almost a week, and then pick it up to find that it’s still well within spec for timing (which is +/- 10 seconds per month). Most mechanical watches become less accurate as their power reserve winds down, but Grand Seiko has taken steps to prevent that with this new caliber. 

Dual barrels maximize torque through the entire 5 day power reserve.

Although the 9RA5 is thinner than the comparable 9R6 by nearly a full millimeter (thanks to a redesign and repositioning of the famed “Magic Lever,” which allows the rotor to wind the watch when swinging in either direction), you’ll forgive the SLGA001 for not taking full advantage of the new caliber’s svetle dimensions. This is, after all, a professional diver rated to 600 meters of water resistance, suitable for saturation diving and virtually anything else under the sea. The titanium case comes in at 46.9mm in diameter, and is 16mm thick. With big, faceted lugs, a chunky bezel, and a super-sized handset, everything about the SLGA001 leads one to think that it will have wrist presence to spare.

Grand Seiko gets a lot of attention for their dressier watches, that take full advantage of the intricate zaratsu polishing the brand is known for, but their sports watches and tool watches are sometimes forgotten about. That’s unfortunate, because they’re made to the same high standards as the rest of the line, and have a unique charm all their own. And given the unique technical properties of their advanced Spring Drive movements, it makes sense that the first time we see the 9RA5 that it’s housed within a watch that could very well be used by professionals who will depend on it to get them through a dive alive. Spring Drive is all about reliability and precision, and those qualities are absolutely essential in a watch that’s actually meant for diving. 

That said, this particular diver may be snatched up by collectors. It’s a limited edition of 700, with a retail price of $11,100. Not exactly a grab-and-go tool, for most. Still, as an example of the high end of what Grand Seiko is capable of in the sports watch category, the SLGA001, with its updated Spring Drive movement, is undeniably impressive. Grand Seiko

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Zach is a native of New Hampshire, and he has been interested in watches since the age of 13, when he walked into Macy’s and bought a gaudy, quartz, two-tone Citizen chronograph with his hard earned Bar Mitzvah money. It was lost in a move years ago, but he continues to hunt for a similar piece on eBay. Zach loves a wide variety of watches, but leans toward classic designs and proportions that have stood the test of time. He is currently obsessed with Grand Seiko.