The Greubel Forsey Double Tourbillon 30°, presented in 2004, is the brand’s first production watch. It has two tourbillon cages, one inside the other: the inner one makes a turn in one minute and sits within an outer cage that turns in four minutes, and the whole assembly is inclined at 30 degrees. The case is in gold or platinum and the movement is hand-wound. I did not find a reliable single source for the case size, so it is not given.

The inclination is the point: a tourbillon is meant to average out the effects of gravity on the escapement, and Greubel Forsey argued that tilting it at 30 degrees better matches the positions of a watch worn on the wrist. Robert Greubel and Stephen Forsey had worked with Renaud et Papi before founding their own firm.

The watch is regarded as a landmark of high-end contemporary watchmaking and brought the brand quick recognition, including prizes from the watchmaking industry. The Double Tourbillon 30° remains a part of Greubel Forsey’s collection in updated versions.