Since 2006 the name DATOGRAPH PERPETUAL has stood for the ingenious combination of flyback chronograph and perpetual calendar. Ten years on, this fascinating timepiece is now available with an added tourbillon – although at first glance, the only clue is in the name on the dial. That is because the tourbillon can only be seen by looking through the sapphire-crystal caseback.

For the watchmakers, integrating this popular mechanism into this exclusive timepiece was a much more challenging task than might be expected. That is because the 729-part calibre L952.2 movement was not simply constructed module by module. Instead, A. Lange & Söhne decided on a more elegant but more complicated solution: within the movement, which was rebuilt from scratch, the three complications that give the watch its name were all connected to form an integrated whole.

The chronograph is equipped with a column-wheel mechanism, a precise jumping minute counter and a flyback function. The jumping perpetual calendar is paired with a moon-phase display and a Lange outsize date. And a glance through the sapphire-crystal caseback into the movement – hand-decorated in accordance with the highest Lange standards – makes it clear how the chronograph mechanism was arranged around the tourbillon. Thanks to the patented stop-seconds mechanism, the balance wheel is momentarily brought to a standstill when the crown is pulled, so that the watch can be set with one-second accuracy.

The sophisticated nature of the watch's construction is also reflected in its design: the clearly structured black dial of this model – which is limited to just 100 watches – is easy to read despite the density of information it displays.