This timepiece is a vintage Omega Seamaster 166.0209, an automatic calendar watch. It is powered by the renowned Cal. 1020 automatic movement, featuring a double calendar, stop-seconds, and quick-set functions. The dial exhibits a distinct tropical dial weathering effect and even yellowing with age. This discoloration caused by ultraviolet light and time is often considered a unique mark of its era in the world of vintage watch collecting. It is a distinctive feature of this watch and makes it highly collectible. 【Brand】Omega 【Series】Seamaster 【Model】166.0209 【Movement】Original 1020 automatic movement 【Crown】Original crown 【Crystal】Omega original crystal, with Ω marking 【Case Diameter】35mm (excluding crown) 【Dial】Original dial 【Strap】Replacement steel strap and buckle, can be worn up to 20mm wide 【Year】Approx. 1978 【Condition】Timekeeping and functions are all normal 【Remarks】Manual + automatic. Pulling the crown out to the first position adjusts the date up and down; pulling the crown out further to the second position and rotating the hands counterclockwise adjusts the day of the week.