Model: Calatrava Reference: 3445/6 Date: Manufactured 1971, Purchased September 29th 1977 Movement: 37-jewel Cal.27-460M PM automatic, adjusted to heat, cold, isochronism & 5 positions, 18K gold rotor, Seal of Geneva, No.1231659 Dial: Sunburst blue sigma, applied white gold baton hour markers, outer minute divisions, subsidiary seconds at 6, polished pointed baton hands Case: Brushed and polished round, textured bezel, screw down back, No.325909 Strap/Bracelet: Integral smooth link Buckle/Clasp: Signed folding clasp Signed: Case, dial & movement Size: 35mm Accompaniments: Extract from the Archives 注脚 In 1961 Patek Philippe launched the 3445/6 in four different metal options - yellow gold, white gold, pink gold and platinum. Each material had varying dial options and could come either with a leather strap or metal bracelet. The current example dating from 1971 features a highly attractive blue dial complimented by its solid 18K white gold case and bracelet. The 3445 was the first automatic watch by Patek Philippe to have a date. The current example is fitted with a 'sigma dial', a nickname for watches that feature a lowercase letter sigma σ from the Greek alphabet below 6 o clock. This signifies the hour markers being made out of 18K white gold. Introduced in the 1970s, this feature can be found on watches as late as 2003.