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When The Sun Wears A Tourbillon.
In 1986, Audemars Piguet decided to enter the tourbillon wristwatch game and completely rewrite it. The Reference 25643, better known among collectors as the “Sun Ra,” was the first self-winding tourbillon wristwatch produced in commercial series. And at 4.8mm thick overall, it was (and arguably still is) the thinnest of its kind. A world first, hiding in plain sight.
At the heart of the watch is the Caliber 2870, a movement that looks like it belongs in a science museum display case. The tourbillon carriage is titanium — the first time anyone had used the metal in tourbillon construction — measuring just 7.2mm across and 2.5mm high. There’s no conventional winding crown breaking the clean case lines; instead, you set the time with a flush back crown and wind it with a swing of the wrist, thanks to a platinum–iridium hammer weight visible at 6 o’clock.
The dial is a love letter to both ancient Egypt and avant-garde design. The tourbillon is rendered as a stylized sun, radiating gilt rays across the surface — a motif inspired by relief carvings of Pharaoh Akhenaten and Queen Nefertiti. It’s history, mythology, and horology in one frame. And it’s done with such restraint that it’s almost easy to miss how bold it is. Almost.
Sized at 28.5mm x 32.5mm, the soft rectangular (almost elliptical) case sits like an ancient gold ingot smoothed by decades of wear. The black alligator strap with its 18K gold AP buckle keeps the look formal but not fussy — like a jazz musician in a perfectly tailored suit. Flip it over, and the back is engraved “Tourbillon automatique,” the jewels on display for the sake of thinness and, frankly, flex.
This is the kind of piece that makes seasoned collectors pause. Not because it seeks the spotlight, but because it belongs there.
Excellent overall vintage condition with light, honest wear consistent with age.
18k yellow gold case retains sharp edges and shows minor surface marks.
Gilt sun-ray dial is clean, with crisp printing and well-preserved applied markers.
Caseback engraving and hallmarks are deep and legible.
Hands are intact with no aging; sapphire crystal is clear.
Original AP black alligator strap in very good condition with matching 18k yellow gold AP buckle.
Movement is clean and running, hammer-winding system functioning as intended.
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