Launched in 1986 just as the Quartz Crisis was beginning to peak and Swiss watchmakers were continuing to go defunct, the Audemars Piguet Tourbillon Automatique ref. 25643BA was debuted as the world’s first automatic tourbillon in an effort from AP to continue pushing high horology. Powered by the ultra-thin cal. 2870 movement, which uses the ref. 25643BA’s caseback as its movement baseplate – as evidenced by the visible presence of six rubies on the caseback, the ref. 25643BA stands an incredibly thin 5.5mm tall – impressive even by today’s standards for an automatic tourbillon. Offered in a rounded rectangular 18kt yellow gold case, the ref. 25643BA features a stunning golden champagne dial whereby its tourbillon aperture, placed at 11 o’clock, serves as the central point of its display with an Art-Deco-inspired sunray pattern radiating across the rest of the dial. Featuring a blued steel hammer weight with applied ‘AP’ initials that swings back and forth like a pendulum in a crescent-shaped aperture at 6 o’clock, the ref. 25643BA is a stunning expression of how unique 1980s high-end watchmaking could be outside of the scope of quartz watches.

An impressive horological feat even by today's standards, the ref. 25643BA was a marvelous step forward for watchmaking at the time of its release in the 1980s, and the industry has been impacted ever since, with the proliferation of its eponymous complication.