The Omega Seamaster "Big Blue" (Reference 176.004) is a historic 1970s diving chronograph, distinguished as the world's first automatic diver's chronograph that was truly water-resistant and functional to depths of 120 meters (400 feet). Produced between approximately 1972 and 1977, its massive, helmet-shaped case and vibrant blue aesthetic have made it a high-target collector's piece.

• Case Size: 44mm diameter (often listed as 44x52mm) with a substantial thickness of 17mm to 19mm.

• Movement: Omega Caliber 1040, the brand's first automatic chronograph movement.

• Water Resistance: Rated for 120m / 400ft.

• Features: Includes a 24-hour indicator at 9 o'clock, a 60-minute central chronograph hand (orange arrow), a 12-hour recorder at 6 o'clock, and a date window at 3 o'clock.

• Bezel: Unidirectional rotating bezel with a blue insert.