The IWC Portugieser Constant-Force Tourbillon reference IW5901-02 was made in 2016 as a unique piece. It features a Platinum case and a Grey dial. Inside ticks the hand-wound caliber 94800.
IWC manufactured 94800 calibre (94000-calibre family) is a hand-wound movement with a tourbillon escapement. A patented constant force mechanism is integrated into the tourbillon, ensuring a stable amplitude of the balance - visible through 1 second jumps of the tourbillon. After having run for 48 hours, the constant force mechanism is decoupled and the tourbillon will move in regular 1/5th of a second intervals. It furthermore features a day/night indication, double moonphase display and a 96 hour power reserve.