The present watch is an historically and highly important watch, and is the creation of twogreat engineers: Maurice Grimm and André Beyner. Skilled watchmakers, the two are responsible for having realized several impressive technological advances in watchmaking, including what was at the time the thinnest watch ever made, the “Delirium”.

With this prototype, they succeeded in pushing watchmaking’s boundaries, as it was the world’s first ultra-thin tourbillon incorporating automatic winding. At only 2.7mm thick they established a record in thinness by integrating the movement with the case back. The implementation of the rotor was another challenge, resolved by the novel use of a “hammer” winding system. A heavy oscillating mass made of platinum swings through an arc limited by the width of the case, permitting the watch to be wound via the motion of one’s wrist. This project was acquired by Audemars Piguet, which subsequently launched their groundbreaking caliber 2870 in 1986. Housed inside reference 25643 with an overall thickness of just 4.8 mm, the caliber 2870 was a milestone in the history of watchmaking as it was, at the time, the thinnest serially produced tourbillon wristwatch ever made. The present lot is presented with a large folder containing the original drawings of Maurice Grimm describing the construction of the movement and each component. A true piece of watchmaking history, the present lot is a rare opportunity for the savvy collector.