In the 1950s, André Beyner (1927-2023) was at the forefront of electronic clock development at Ebauches SA, pioneering the use of transistors in timekeeping devices as early as 1958. Alongside Maurice Grimm, his visionary approach led to the creation of the ultra-thin Delirium watch, launched in 1979. This innovative design integrated the case back with the main plate, drastically reducing the watch’s thickness. Not only did this set a new record for slimness, but it also paved the way for the design of the Swatch watch, introduced five years later.

Fruit of another collaboration between Andre Beyner and Maurice Grimm, the project was known under code name "P 29". Following the quartz crisis, the goal of the project was to create an ultra-thin tourbillon wristwatch (4.8 mm thick). With some assistance from Valjoux, they produced a prototype of this ultra-thin movement and presented it to several companies, including Audemars Piguet and Omega, to gauge interest in bringing it to market. In 1982, Georges Golay, who had previously approved the Royal Oak and the ultra-thin perpetual calendar, recognized its potential and acquired the project for Audemars Piguet. This led to the launch of the groundbreaking Caliber 2870 in 1986, housed inside reference 25643. The project ultimately became the first automatic Tourbillon wristwatch ever produced. At the time, it was the thinnest serially produced tourbillon wristwatch ever made, marking a milestone in horological history.

Acquired directly from the original family of Mr Beyner, this prototype was the first ever made bearing the number 1. A unique opportunity to purchase a milestone watch made by one of the most recognised watch engineers ever that marked a significant step towards the return of mechanical wristwatches.