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.
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 delivers a constant amount of energy to the escapement every ten seconds, ensuring that the balance always oscillates with the same ideal amplitude, resulting in consistently superior precision from day one to day 31.
The Lange 31’s sapphire exhibition caseback offers a glimpse of the constant-force device in action: the triangular cam attached to the fourth-wheel arbor controls the mechanism with a cleverly designed pivoting lever that recharges the remontoir spring with fresh energy every 10 seconds. The powerful mainsprings — each 185 centimeters long — are tensioned with a separate key that inserts into a square socket in a recess of the casback. Its technical features include an integrated backstop ratchet for smooth and easy winding and a torque limiter that prevents unintentional overwinding of the springs. Of course, as most would expect from an A. Lange & Söhne in-house movement, the decorations and finishes are as impressive as the technical innovations, among them plates made of untreated German silver and enhanced with Glashütte striping, a hand-engraved balance cock, 62 jewels, and three screwed gold chatons.
All this inward complexity is reflected in an elegant outward simplicity. The gray dial, made of solid silver and traversed by rhodiumed gold hour and minute hands, is dominated by the large, arc-shaped power-reserve indicator at 3 o’clock, with a “31” at the upper end and a red “0” at the bottom. Directly under the outsize date display in a double-window aperture at 10 o’clock, a hallmark of the Lange brand, is the inscription “Monats Werk” (“monthly movement”), a further reminder of this watch’s signature attribute. Small seconds appear unobtrusively on a subdial at 6 o’clock. The new Lange 31 is mounted on a hand-stitched dark brown alligator strap with a deployant buckle made of white gold. Currently available, it is priced at $140,500.