Designed and developed by Cartier, the caliber 9909 MC includes several original functions: a lateral cities disk, a retrograde time-difference hand, "Home" time indicated by a 24-hour hand, and adjustment for summer/winter time. A unique feature of this model, the lateral cities disk is an integral part of the movement and is easy to use when moving across time zones. The originality and practicality of these functions make this a timepiece of choice for the modern traveler.