Longines L2.537.4.72.6 Ultra-Chron ClassicULTRA-CHRON CLASSIC, L2.537.4.72.6, automatic watch, Ø 37.00 mm, stainless steel.Date, self winding mechanical movement beating at 36'000 vibrations per hour, with a monocrystalline silicon balance-spring power reserve up to 52 hours.Water-resistant to 5 bar, scratch-resistant sapphire crystal, with several layers of anti-reflective coating on both sides.Sunray silver dial.Stainless steel bracelet, with double security folding clasp with micro adjustment system.