A. Lange & Söhne L034.1

Hand-wound movement with an unprecedented 31-day (744 hours) power reserve. Energy stored in large twin mainspring barrel consisting of two stacked barrels with 25mm inside diameter. Each accommodates a 1850mm long spring - up to ten times longer than conventional wristwatches. When fully tensioned, stores more than 3 joules of energy. Features patented constant-force escapement ensuring consistent amplitude.