25643BA Audemars Piguet ‘Sun Ray’ Tourbillon

If the tourbillon is often utilized a bit garishly (and let’s be honest, it is), it certainly didn’t start that way. Despite almost no one knowing the reference and it rarely receiving a mention at all, this ‘Sun Ray’ ref. 25643 was the world’s first self-wound tourbillon wristwatch and the first to be serially produced. It is so eclectic newer enthusiasts might mistake it for the whimsy of Cartier. But no, that’s just what used to happen when AP weren’t the Royal Oak company. It’s technically astounding, very unlike anything before or since in design, and a true innovation. Perhaps the design is just too challenging for some, but you at least can’t call it boring. Unlike most of AP today. Brands dared in the 80s.

And it is full to the brim with interesting details. Thinness was the priority here, and it certainly hit that mark at 5.3mm. It was the thinnest automatic tourbillon for decades, superseded by Bulgari and only by 1mm. To achieve this, there is no traditional bottom plate. The great train jewels are set directly in the caseback. This is very like a form of engineering I know from the car world, where in F1 or superbikes, manufactures will use the engine block as a stressed member of the chassis to eliminate weight. And you’ll note no crown at 3. To keep symmetry, AP made this a back-winder, with a hammer under the movement at 6 to wind it. Its calibre 2870 had an incredibly difficult-to-make titanium tourbillon cage to reduce mass and power demand, the first of its kind. This watch would still be impressive if released today. It was a loss leading project that only was green lit to show the world that AP had technical ability to rival the best, much like the RD series today.

But then there’s the sheer strangeness of the dial. Inspired by a famous carving of Pharaoh Akhenaten, this from a time when the world was a bit Egypt obsessed and King Tut’s museum exhibition was a groundbreaking commercial success. One other detail on this side is the AP signature, which isn’t on the dial but crystal underside, so you get a shadow in direct sun. I’ve always wondered if this was sun ray inspired as well. So it’s not just unique mechanically, it’s bizarrely Egyptian on top of everything. 401 examples were made, numbered in series. Most look like this, but there are also a few platinum with mother of pearl dials and even three known with an integrated bracelet. It’s the sort of watch that makes you wish AP would reference their rather immense history more often.

These don’t come up terribly often but are always fun to see. They’ve screamed from 20K or thereabouts pre-Hodinkee (and Jack’s excellent article on the subject) to around double that today. As collectors increasingly focus on scholarship, historic significance, and intrigue, I can only imagine this will be come increasingly collectible. But that’s shooting myself in the foot, because I don’t own one yet and would quite like to. In any event, this one is great. Full case and sharp back engravings, clean dial, running well. It comes from a well-regarded London retailer.