The first generation Zeitwerk is something really quite special. Introduced at SIHH in 2009, it was the first mechanical wristwatch ever to boast jumping hours and minute numerals, a bizarre marriage of traditional Glashütte watchmaking as applied to a very challenging and modern problem. Yellow gold was produced for just four years and, though not limited, its production was far lower than the white gold, speculated to be around the limited 200-example platinum's production. And it hasn't been made since. This first generation ref. 140.021 is still the only yellow gold Zeitwerk to ever appear in the main model line, one which has been rarely seen since production and only once at auction at time of writing.

The Zeitwerk was inspired by the Dresden Opera House clock built by Johann Gutkaes with help of one Ferdinand A. Lange in 1841. Its mechanical 'Five-Minute' clock was the inspiration for the Lange 1 date window, but even moreso the Zeitwerk's inline apertures. It was Blümlein who first had the idea of creating a digital watch, but a separate team that carried out the challenge.

That challenge required over 5 years of development, according to Anthony de Haas. The jumping discs were made possible through the largest mainspring A. Lange & Söhne had made and a very intricate constant force remontoir, the work of Jens Schneider. Because it takes much more energy to turn all three discs than just one, a windflüge (windbrake in English) mechanism was invented to deplete excess energy when full power is not required. It works like a fan to bleed off the excess energy through air resistance and not damage the single disc with too much power. In wearing, you can feel a snap of energy when the remontoir releases its energy to move the massive discs. The manual Caliber L043.1 is like nothing else, which becomes obvious when you study the caseback with its anchor bridge that carries the constant force mechanism, escapement, balance wheel, and winding gears, all hand-finished to an exceptional standard.

Having studied many previous digital pocket watches and clocks, the decision was made to innovate in design with an exposed bridge on the dial, which gives the Zeitwerk its distinctive winged shape, penned by Nils Bode. The case was made as thin as was possible for all the mechanical complication, 41.9mm at 12.6mm thin. The unique crown at 2 was a direct consequence of movement architecture, while the rest was Lange's usually teutonic 3-piece construction with contrast finish.

The Zeitwerk has since seen a considerable updates and model line expansion, but yellow gold has not returned. You'll find the specialty Lumen and Striking watches in Honeygold, but the time-only second generation Zeitwerk is now only available in pink gold and platinum; yellow gold hasn't been seen since and probably won't be again. This is a Zeitwerk from a quite different A. Lange & Söhne than what it is today, a watch which was easily their most audacious project ever in 2009. It captured Lange's traditionally teutonic and revolutionary spirits in full measure, backed up by one of the most innovative calibres of its time, to create a watch that moved Glashütte into a new era.

This 140.012 presents in excellent overall condition. Its case has a light patina with superficial wear and some hairline marks on its mirror finish bezel and lug upper. There are no significant or deeper marks. It is mechanically and operationally perfect, serviced last year at A. Lange & Söhne with receipt included. It comes on the pictured grey suede strap with its original signed buckle.

This watch is modeled on a relatively large 7.7 inch wrist.

• Brand: A. Lange & Söhne
• Model: Zeitwerk
• Reference: 140.021
• Size: 42
• Year: c. 2009
• Case Material: 18k Yellow Gold
• Movement: Manual Caliber L043.1
• Scope: Watch, A. Lange & Söhne Certificate & Proof of Origin, Original Buckle