Patek Philippe. Rare et insolite montre bracelet en or jaune 18K (750) mouvement mécanique, antimagnétique Patek Philippe. Rare and unusual 18K gold manual wind antimagnetic wristwatch Calatrava, Ref 2509, Circa 1958Patek Philippe. Rare et insolite montre bracelet en or jaune 18K (750) mouvement mécanique, antimagnétiquePatek Philippe. Rare and unusual 18K gold manual wind antimagnetic wristwatch Model: CalatravaReference: 2509Date: Circa 1958Movement: 18-jewel Cal.27-AM400 manual wind, adjusted to heat, cold, isochronism and 5 positions, seal of Geneva, No.733072Dial: Cream, gilt applied faceted and pointed baton hour markers, silvered outer minute divisions, subsidiary dial for seconds at 6, gilt faceted lance handsCase: Brushed and polished tonneau form, screw down back, inner Geneva stamp, No.2625848Strap/Bracelet: Green crocodile leather Buckle/Clasp: Signed 18k gold buckleSigned: Case, dial & movementSize: 35mm Weight: 50,74gIn 1950 Patek Philippe launched two larger sized Calatravas - references 2508 and 2509. Reference 2508 featured centre seconds and Reference 2509, as with the current lot, has subsidiary seconds.Patek Philippe first introduced the Amagnetic movement in 1958. To signify this they added AM to the calibre number and on the dials of the calibre 3417 wrote in large cursive script Amagnetic. This has become a much sought after model combining the usual classic aesthetics we are used to from Patek Philippe with the scientific invention that we are used to from 'tool' watch manufacturers.