Some watch enthusiasts adore the daily ritual of winding their mechanical timepieces; others would prefer to wind their watches only as frequently as they pay their electric bill. It is for this latter group that A. Lange & Söhne created the groundbreaking Lange 31 in 2007. The watch, which amasses an unprecedented 31-day power reserve, debuts in an all-new edition this year, with a white-gold case and slate gray dial. The new Lange 31, which debuted at SIHH 2017, is this week’s Watch to Watch.
 
A. Lange & Sohne Lange 31 – front

This latest iteration of the Lange 31 ? the first and still only mechanical timepiece with a power reserve lasting an entire month ?  is limited to 100 pieces. Its round, white-gold case measures 45.9 mm in diameter and 15.9 mm thick and contains the manual-wound Caliber L034.1, which was engineered by Lange’s expert watchmakers to maintain a top-notch rate accuracy over its entire 744 hours of winding autonomy, from the first to last day. They accomplished this amazing technical feat with a constant-force escapement, positioned between the two mainspring barrels and the going train, to deliver a uniform level of torque throughout the entire running period. In most other movements with lengthy power reserves, the enormous amount of torque built up when the movement is fully wound declines gradually toward the end of the power-reserve period, thus affecting accuracy. But Lange’s constant-force device deli...