The 1815 Moonphase model was created to celebrate Emil Lange's 150th birthday in 1999. It was made in a limited series of 150 examples in platinum and 250 in pink gold and produced between 1999 and 2000.
Seven gold appliques represent the Big Dipper constellation, one of the most distinctive asterisms in the sky. Mizar and Alcor are portrayed in the middle of the Big Dipper's handle. Since Alcor is so small, the ability to distinguish the two stars was held as a measure of good vision in medieval times.
The moon position is automatically adjusted twice a day and will deviate from the moon's actual orbit by only one day after 386'435 days or 1058 years of uninterrupted operation.