Patek Philippe. An 18K gold automatic calendar bracelet watch

Calatrava 'IOS', Ref: Ref:3565/1, Circa 1965

Model: Calatrava 'IOS'
Reference: Ref:3565/1
Date: Circa 1965
Movement: 37-jewel Cal.27-460M automatic, adjusted to heat, cold, isochronism and 5 positions, gold rotor, Seal of Geneva, No.1128280
Dial: Sunburst champagne, black Roman numerals, date aperture at 3, black pointed baton hands
Case: Polished round, snap on back, 'Directors Award' engraved to back, No.2674042
Strap/Bracelet: Integral mesh link
Buckle/Clasp: Signed 18K gold sliding clasp
Signed: Case, dial & movement
Size: 35mm
Accompaniments: Patek Philippe box

These watches were made to order for the company IOS, Investors Overseas Services Limited, themselves a major investor of Patek Philippe. If an IOS trader surpassed their turnover threshold of $1 million dollars, they would receive one of these watches in recognition and reward. The production number has never officially been disclosed, but is thought to be around 1500 watches.