This display unit platinum A. Lange & Söhne Lange 31 Ref:130.025F is new unworn. It comes with two winding key, box and warranty booklet dated in 2013. 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!