The Ingenieur Perpetual Calendar Digital Date-Month is the flagship of the Ingenieur family. The design, with its simple round case and the polished bezel, is inspired by the first generations of Ingenieur models from the 1950s and 1960s. This timepiece has a case measuring an imposing 45 millimetres made of titanium, and is limited to 100 individually numbered pieces. It has a slate-coloured dial and black hands with luminescence. The perpetual calendar displays the date and month in large digital displays on the dial, and is mechanically programmed to recognise the different lengths of the months and even adds a leap day at the end of February every four years. A chronograph with flyback function is an additional feature of the IWC-manufactured 89801-calibre movement. The rotor of the automatic winding system is made of solid 18-carat gold and can be seen through the transparent sapphire glass back.