Not too many brands have not only the staying power of a Patek Philippe, but the ability to continue to improve and refine with age. Marking their 175th anniversary, Patek Philippe does so with the utmost elegance, releasing a limited number of watches that are sure to be highly coveted. Both under the new Patek Philippe World Time Moon model, there are two versions of this special edition release, both with realistic moon phases displayed at the center of the dial. The first, Reference 5575, seen in the preview image above, is the men's edition with a smaller bezel, while the Reference 7175, adorned with diamonds, is the lady's model. Both are powered by an all-new caliber 240 HU LU, developed specifically to power the world-time function and the moon phase display simultaneously and built with 270 individual parts. The men's case will be made of 18k white-gold while the lady's in rose gold, adorned with 70 diamonds totaling .6 carats. And, the Pièce de résistance, both include solid case backs engraved with "PATEK PHILIPPE GENEVE 175e Anniversaire 1839 - 2014." For more on where you can find them and on the timepieces themselves, visit the Patek Philippe online site.