Double Tourbillon 30° Secret is a luxury wristwatch by Greubel Forsey.

See:

• Greubel Forsey Double Tourbillon 30°

Greubel Forsey's first invention, presented in 2004, was an innovative double tourbillon mechanism (DT30), with one tourbillon – inclined at 30° and rotating in 60 seconds – inside another rotating every four minutes, to average out gravity-induced errors on the oscillator.

This model has, as the name already tells, a closed dial merely hinting at the sophisticated mechanism beneath.