The big-date display, which can be patented, works by means of a “ones” ring bearing the digits 0 through 9 plus a “tens” cross with the digits 1 through 3 and a sterile field. A unique challenge for the engineers was to make sure that the calendar changed correctly at the endings of months with 31 days. For those months, the “ones” ring needs to stay motionless during the night prior to the first of the new month, while the “tens of thousands” cross legged through 90 levels to deliver its clean segment into perspective. A button on the other hand is used to fix the date screen at the end of February, April, June, September and November.A. Lange & Söhne released its initial self-winding watch, the Langematik, three years later it established the Lange 1. To raise the motion’s winding efficiency, the good gold strand in the Langematik has an outer platinum segment. A reverser mechanism allows the rotor to convey energy to the mainspring in the two directions of rotation. To minimize friction, Lange’s watchmakers added three micro ball bearings to the reduction gearing.
Anthony de Haas speaks about the development process and why the 1815 is so reminiscent of the early design of the pocket watches made by Ferdinand Adolph Lange.