Greubel Forsey Quadruple Tourbillon Secret

One of the most rare and most interesting watches from what is, IMHO, the best watch brand on Earth. The Quadruple Tourbillon was GF's second invention. It combines two double tourbillons that are connected via a differential to average out errors and provide the greatest possible isochronism. In the case of the Secret, this entire mechanical ballet becomes the secret of the owner, only visible through the back. The front has a beautiful, uncut, black gold dial with hands that indicate the state of each tourbillon and the averaged seconds. It's a combination that makes the watch extremely precious feeling while remaining very wearable and full of class.