This is a whte gold A. Lange & Sohne Datograph Perpetual Calendar Chronograph 410030. The solid case is polished, with a sapphire crystal display case back with 6 screws. It has a grey, solid silver dial and applied Roman numeral hour markers. The white gold sword hands have luminous inserts, and the black alligator leather strap has a matching white gold tang buckle. It's wat er resistant to 30 meters. A large date aperture is at 12 o'clock, and the moon phase sub dial is at 6 o'clock. There is a 30-minute fly back chronograph. The sub dial at 3 o'clock indicates the month, and has an inset leap year indicator. The day of week sub dial is located at 9 o'clock with an inset am/pm indicator. The date can be corrected by using the rectangular push button on the case edge at 10 o'clock; each complication can be independently corrected by using the recessed corrector buttons. The chronograph has a fly back function that allows the stopwatch to be instantaneously restarted for continuous timing; you don't have to stop, reset, and then restart the chronograph. The minute hand of the chronograph jumps in one-minute increments instead of continuously moving, giving a more accurate reading of the timing function. The outer track has a tachometer Scale. The case, dial, and movement are all signed. The A. Lange-Sohne calibre L952.1 movement is rhodium-plated; it has 45 jewels, and is comprised of 556 parts. The mechanism oscillates at 18,000 vph, and the movement has a power reserve of approximately 36 hours.