The Omega Speedmaster Triple Date (Reference 3520.50.00), widely known as the Speedmaster Day-Date or Mk40, is a highly complex, 39mm automatic chronograph produced by Omega during the late 1990s and early 2000s. It packs a full triple calendar complication into a more compact "Reduced" footprint, maintaining the iconic aesthetic of the standard Speedmaster Professional while providing enhanced daily functionality.
Dial Anatomy & Complications
  The matte black dial is highly dense but meticulously organized to present eight separate hand functions and two calendar apertures: 

• • Central Hands: Displays standard hours, minutes, and the central chronograph seconds. A unique fourth central "pointer" hand features a red crescent tip that points to the date scale on the outer rim of the dial.

  • 12 O'Clock Sub-dial: Features a 30-minute chronograph counter alongside dual windows displaying the Day of the week and Month.

  • 9 O'Clock Sub-dial: Houses the running sub-seconds hand and an integrated 24-hour indicator (AM/PM hand).

  • 6 O'Clock Sub-dial: Contains the 12-hour chronograph counter. 

Movement & Mechanics
  Unlike standard Speedmaster Reduced models that use modular ETA movements, the reference 3520.50 is powered by the Omega Calibre 1151. This caliber uses an integrated, highly reliable Valjoux 7751 base configuration.

• Date Changes: The pointer date and month are advanced by pulling the crown to the first position.

• Day Correction: The day of the week window is updated using a dedicated, recessed quick-set pusher located on the side of the case at the 10 o'clock position.