Introduced in 1994, Patek Philippe's reference 5004 was in production only until 2009. Available in all three colors of gold, platinum and a later series in steel, this perpetual calendar chronograph watch remains particularly desirable to collectors because it features a split-second complication. Recognizable by its prominent oversized co-axial crown, it was, along with the chronograph-only reference 5070, the last of Patek Philippe’s complicated watches to use an outsourced caliber base, in this instance Nouvelle Lemania, which was specially developed for Patek Philippe and finished in their workshops.