Case material: Rose gold; Charge: Manual; Conditions: New Presentation condition : With boxes and all papers; Model: Lange 31 Price on request Gmtbroker Reference: 130.032 A. Lange & Sohne 130.032 Complete Details: 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 is only half of the challenge, as the torque in the spring will fluctuate considerably (especially in watches with larger power reserves), which in turn will have a negative impact on accuracy. Thus an equally challenging feat is   to take the stored energy and transfer it to the movement in a controlled and uniform manner. Enter the LANGE 31, Lange presents   the world’s first mechanical wristwatch 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 between the twin 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! Another practical feature is the “Key Winding Mechanism” where th