SIHH Preview: A. Lange & Söhne Datograph Up/Down Written byWatchTimeDecember 22, 2011 Many collectors consider A. Lange & Söhne’s Datograph a must-have timepiece. This newest version, with several enhancements, demonstrates that Lange’s engineers can improve on an already-excellent design. The new model features a 41mm platinum case, an extended 60-hour power reserve, a power-reserve indicator, and a proprietary oscillation system. Find wallpaper images inside. When it debuted in 1999, the Datograph was a sensation. The functions, aesthetics, and perhaps above all the movement, generated excitement the world over. A high-resolution image of its caliber L951.1 became desktop wallpaper for collectors wherever the internet reached. The dial, with its instantly-recognizable outsize date and the two bright subsidiary dials, assured legibility and signaled the owner’s appreciation for fine watchmaking. The new Datograph Up/Down embodies these features as well. What meets the eye first is the larger case. The new 41 millimeter size provides added prominence on the wrist. The Roman II, VI and X have been replaced with Rhodiumed gold baton hour markers to enhance the clear design and identify the watch as a member of the Saxonia family. The date-display aperture was adjusted by 4% to match the bigger size of the case and the maintain the balanced dial architecture. The “Up/Down” designation refers to the power reserve indicator at 6 o’clock, which reliably tells the owner how much running time remains available. When the display hand enters the red zone after three days, it it necessary to supply the caliber L951.6 movement with fresh energy. A larger mainspring barrel generates the additional 24 power-reserve hours compared with the previous model. The large balance developed by Lange and crafted in-house has six eccentric poising weights that can be precisely adjusted to fine-tune its rate accuracy. It is powered by a balance spring, also developed and crafted on site by Lange. To assure optimized rate values at its classical frequency of 18,000 semi-oscillations per hour, the spring is carefully matched to the characteristic of the movement. Among many other technical refinements, the Datograph Up/Down features the technically complex flyback function. Originating from the early days of aviation, this mechanism makes it possible to instantly preform consecutive time measurements by combining three steps – stop, reset, restart – into one: a single push of a button will stop and reset the Datograph Up/Down in the middle of an ongoing time measurement. When the button is released, a new time measurement is immediately initiated. The sapphire-crystal caseback reveals one of the most beautiful chronograph movements ever made. Highlights include the precisely jumping minute counter that guarantees exact time measurement, the column wheel that controls the chronograph functions, and the whiplash spring-secured precision beat adjustment system on the hand-engraved balance cock. All surfaces are meticulously finished by hand. As this story is being published, the Datograph Up/Down price is still to be determined. The images below may be significantly enlarged with a click.