On very rare occasions does Grand Seiko create unique versions of its watches. But it has done so with a unique version of the Kodo Constant-Force Tourbillon – the one-off reference SLGT001 – that will go under the hammer at Phillips’ New York auction December 11, with some proceeds from the sale going to a children’s charity.

Anyone who read our earlier in-depth, two-part story on the Kodo (part I covers the watch and part II its technical features) will understand the the impressive technical achievement that is its movement. The SLGT001 has all of that, but in a unique execution specifically for the auction.

Engraved “Unique Piece No. 1/1” on the back, the SLGT001 is instantly recognisable as a one-off.

While the standard version of the model has a monochromatic grey palette, the SLGT001 is set apart by its colour: heat-blued and gilded components against rhodium-plated bridges. Most of the screws are blued steel, while the three-armed tourbillon carriage is blued titanium.

And the SLGT001 is also distinguished by its case material. Unlike the standard model that has a case made up of both titanium and platinum, this is entirely in Brilliant Hard Titanium, the brand’s proprietary alloy that boasts a brighter, more silvery hue than most titanium alloys.

A portion of the proceeds from the sale of the SLGT001 will go to the Children’s Heart Foundation. Besides benefiting a good cause, the winning bidder will also get a trip to Japan to meet the team behind the SLGT001 at the Grand Seiko workshop in Shizukuishi, a town in northern Japan.

The SLGT001 is lot 100 in the sale; for more visit Phillips.com.