A. Lange & Sohne Lange 31 White Gold Limited 100 Pieces 130.039 with a Constant-Force Escapement and Double Stacked Mainspring Barrels

The Lange 31 with an amazing 31 day power reserve! One of the most challenging aspects in production of mechanical wristwatches is the duration of the Power Reserve, understandably the longer the Power Reserve the more convenient it is to the wearer. Thus most top brands invest considerable time, effort & funds into developing a mechanism that can store the most amount of energy within the constraints of a wristwatch case size. Storing energy within the constraints of a wristwatch case size is only half of the challenge. Mainspring torque fluctuation (especially in watches with larger power reserves) will have a negative impact on accuracy. Thus an equally challenging feat is transferring the stored energy from the mainspring to the movement in a controlled and uniform manner.

Enter the LANGE 31 with a power reserve of 31 days and a patented constant-force escapement. The double stacked mainspring barrels, each with an impressive 185cm long spring, store the energy. A constant-force escapement situated between the mainspring-barrels and the going-train assures that the balance receives an identical amount of energy every ten seconds, regardless of the state of wind of the springs.

The 45.9mm diameter solid three-body case, curved lugs, and concave cupped bezel, are polished. The dial is rhodium silver with applied faceted 18k white gold hour markers, around a perimeter minute scale. It has polished white gold epee hands, and there is a recessed silver subsidiary running small seconds dial at 6 o’clock. A silver-rimmed double-window quick set Big date aperture is at 10 o’clock, and it’s operated by a rectangular button on the case edge at 10 o’clock. There is a railroad-style scale at 3 o’clock for the 31-day, 744-hour power reserve - the first to last an entire month. It’s water resistant to 30 meters/100 feet, and the 15.9mm thick case, dial, and movement are all signed. 

This A. Lange & Sohne Lange 31 130.025 has a mechanical manual winding Lange caliber L034.1 movement. It’s three-quarter plate with Cotes de Geneve ribbing, and it’s constructed with 62 jewels including 61 rubies and one transparent sapphire. It has 406 components, blued screws, three screwed gold chatons, a whiplash precision index adjuster on a hand-engraved balance cock, and two stacked mainspring barrels with each accommodating an 1850mm spring (10 times longer than a conventional wristwatch). At full tension the twin barrels store over 3 Joules of energy, and the constant force escapement provides continuous energy from the mainspring without any loss of accuracy. The mechanism oscillates at a frequency of 21,600 vph (3 Hz). 

It has an alligator leather strap with a unique foldover deployant buckle, and a scratch resistant sapphire crystal. There is a screw down winding crown, and an exhibition sapphire display case back secured with 6 screws, and engraved with "A. LANGE & SOHNE – GLASHUTTE," a serial number, and several hallmarks. There is a circular keyhole for the winding key system on the solid part of the case back that’s sealed with 3 gaskets insuring water resistance. It is not wound by the crown, but by a winding key that fits into a matching aperture on the case. The provided key has a built-in torque sensor, once the watch is almost fully wound the key senses the increase in tension & will disengage the ratchet key.

The LANGE 31 is the world’s first mechanical wristwatch with a power reserve of 31 days and a patented constant-force escapement. The white-gold model has a grey dial made of solid silver. Limited to 100 pieces, this is a boutique exclusive limited edition.

Reference No. 130.039