The Calatrava Ref. 5227 is an officer’s-style watch, with a dust cover over the caseback, ranked among the most iconic creations of Patek Philippe. The first Calatrava model was launched the year the Stern family acquired Patek Philippe, in 1932. A new development for this style is a special hinge that is located on the inside of the cover, making it invisible. The case and hinge mechanism were developed and produced in-house by Patek Philippe. The dust cover can be engraved to personalize and customise the watch. The caseback has a sapphire crystal window to reveal the self-winding calibre 324 SC, which has a large four-arm Gyromax balance with a Spiromax balance spring made of Silinvar. It beats at a frequency of 28,800 semi-oscillations per hour (4 Hz) to ensure the rate accuracy specified by the Patek Philippe Seal is within the narrow tolerance range of -3 to +2 seconds per day. Hand finishings include round chamfered and polished bridge edges, gold-filled engravings and circular graining. A Calatrava cross adorns the winding rotor, which is made of solid 21K gold to extract as much winding energy as possible from even the slightest motions of the wrist. It is available in 18K yellow, white or rose gold.
