A. Lange & Söhne Grand Complication No. 42500 – An Amazing Story of the Restoration of a Forgotten Horological Treasure

In 2001, a visitor of the A. Lange & Söhne manufactory had handed over an old pocket watch to Jan Sliva (head of the in-house studio for historic Lange pocket watches) and asked for an appraisal. It was particularly large and heavy, and its case was engraved with an intricate motif designed by Professor Graff.

But when Jan Sliva opened the artistically decorated caseback, he discovered a mechanical movement in a very poor condition. All parts were grimy, many were rusted, some were missing altogether, others were broken or so heavily corroded that their original shape could merely be surmised. Only the consummately assembled eight-part enamel dial was, surprisingly, almost in mint condition.

A. Lange & Söhne Grand Complication No. 42500Based on the serial number on a bridge: “42500”, Jan Sliva identified a unique treasure with probably the most complicated, rare, and historically significant calibre that had ever left the A. Lange & Söhne manufactory – and it was the only one of its kind.

The Lange Pocket watch No. 42500 had been sold to a resident of Vienna for 5,600 marks in 1902. This historic pocket watch united a host of fascinating complications such as chiming mechanism with a grand strike and a small strike, a minute repeater, a split-seconds chronograph with a minute counter and flying seconds (seconde foudroyante), as well as a perpetual calendar with a moon-phase display. Its nickel-plated German silver movement in 1A quality consists of an incredible 833 parts. Together with the case, it weighs nearly 300 grams.

It was a watch of inestimable historic value and its restoration would justify any conceivable amount of effort. Jan Sliva and his team decided to study and document the functions and interactions of the individual components on the basis of what was left and to fully restore the functionality of all the mechanisms.

A. Lange & Söhne Grand Complication No. 42500Thus, the declared objective was to conserve as much of the original substance as possible and then to reinstate the function and beauty of the venerable movement. The watch harboured many secrets that would have to be arduously deciphered. It contained a number of parts whose function eluded even the experts. There were components of such intricacy that no one could imagine how they might have been crafted, and even advanced CAD software failed to provide clues.

Other parts which would have to be replaced were so deteriorated that their original geometry could no longer be conjectured.
A. Lange & Söhne Grand Complication No. 42500

Every layer that Jan Sliva exposed raised scores of new questions – for instance how to craft an unusual type of gong for which no specifications existed. In some cases, months went by before a satisfactory solution to a problem could be found. Sometimes, the first try was successful.

In the end, it took until the year 2009 to restore pocket watch No. 42500 to its former splendour. At the SIHH 2010 in Geneva, it was on public display for the first time.

Image Credit: Lange Uhren GmbH

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