Developed on the basis of the Tourbillon Double Balance Spring calibre, this complication opens and closes the dial by the fan-like rotation of two opaque sapphire crystals (FBN Calibre 916.02). A patent has been filed for this invention.
The dial window opens on demand. By pressing a push-button placed on the crown, the two opaque sapphire crystals pivot instantly and reveal the secret dial.
The dial window also opens automatically or in passing. The mechanism is automatically activated for an hour each day, at the specific time chosen by its owner and adjusted by a watchmaker during movement assembly. Just as when the sun is rising or setting, it takes a full hour for the dial to be fully revealed or concealed.