This magnificent Patek Philippe Grand Complication Split Seconds Chronograph & Perpetual Calendar which combines the perpetual calendar complication with a split seconds chronograph complication. The Patek Philippe Ref. 5204 replaces the Patek Philippe Ref. 5004. Both watches feature a split seconds chronograph combined with a perpetual calendar, moon phase indicator and an A.M./P.M. indicator. The new Ref. 5204 has a larger 40mm case, as compared to the 36.7 millimeters of the Ref. 5004. The new Ref. 5204 also has a redesigned dial and hands. Here are the differences: while both watches have manually wound movements the Ref. 5204 has a brand new Caliber CHR 29-535 PS Q movement which beats at 28,800 vibrations per hours and has a 65 hour power reserve. The movement in the Ref. 5004 beat at a slower 18,000 vibrations per hour and had a shorter 60 hour power reserve. In updating the size of the Ref. 5204 to keep up with the times, Patek also made good use of the additional space. A perpetual calendar is a mechanism that automatically takes into account the varying number of days in each month as well as leap years, so that the watch displays the correct date each month without the need of adjustment In addition to the two main complications, the split seconds chronograph and perpetual calendar, the Ref. 5204 has several other complications. The watch displays the day and month