Audemars Piguet 2870

The Caliber 2870 is a groundbreaking ultra-thin automatic tourbillon movement, introduced in April 1986. At only 4.8mm thick, it remains the thinnest self-winding tourbillon ever made - a record that still stands today. The titanium tourbillon carriage is only 7.2mm in diameter, 2.5mm high, and weighs just 0.134 grams - the first use of titanium in tourbillon manufacturing. The automatic winding uses a unique 'hammer' system with a platinum-iridium weight swinging through a small arc (visible at 6:00 on the dial). There is no winding crown - hand-setting is via a small crown in the caseback. The case back functions as the movement's top plate, with gear train pivots running in jewels set into it. The tourbillon rotates counterclockwise once every 50 seconds.