plate. In 1864, Ferdinand Adolph Lange introduced the three-quarter plate in his pocket watches. It replaced the many separate bridges which until then held the arbors of the going train. While this requires more time and effort during the assembly phase, it clearly improves the stability of the movement. Only the balance cock with the oscillation system remained exposed, located beneath a cock. 1867, Jumping seconds hand. In 1867, Lange developed a jumping-seconds mechanisms for a pocket watch, which his sons Richard and Emil adapted slightly and filed for patent ten years later. Further patents include a keyless winding and hands-setting, a system for the removal of the mainspring barrel, a constant-force escapement, a chronograph, an aluminium balance-spring29 and a quarter repeater. 1902, Grand Complication No. 42500. The Grand Complication was made in 1902 as a unique piece. It was sold to Heinrich Schäfer of Vienna for the price of 5600 Marks which at the time was the equivalent of a villa in Dresden, Germany. The watch houses 833 individual parts and features the following complications: chiming mechanism with grand and small strike (grande et petite sonnerie), minute repeater, split-seconds chronograph with minute counter, perpetual calendar with moon phase, flying seconds (seconde foudroyante), and so on. In 2001, the watch came back to Glashütte during a manufacture visit from customers who left it to the hands of the restoration workshop to be repaired. It took a team of five experts and almost seven years to renovate the watch as it was in 1902. In 2010, the restored piece was first exhibited at the Salon International de la Haute Horlogerie (SIHH). The watch is now on permanent loan in the Mathematisch-Physikalischer Salon (Royal Cabinet of Mathematical and Physical Instruments) in Dresden. 1931, Richard Lange's balance spring patent. Elinvar balance spring's introduction was revolutionary because it was removing the effects of temperature over the elasticity of the spring. After Emil Lange's introduction of the nickel-steel balance to Germany, Richard Lange's interest in the metallurgical aspect of watchmaking was awoken. He was the first to realise that adding beryllium to nickel and steel lessened the sensitivity of hairsprings to temperature fluctuations and magnetic fields on the one hand, while improving their elasticity and hardness in comparison with the Elinvar alloy springs. His patent application “Metal alloys for watch springs” in Germany and was granted in 1931. His invention created the base of the