OMEGA Speedmaster Calibre 321

The Speedmaster Calibre 321, reference 311.30.40.30.01.001, is built from a 39.7 mm steel case with a ceramic bezel and paired with a steel bracelet. The black dial is protected by a sapphire crystal and includes a chronograph function with small seconds. It is powered by the manual-winding Omega calibre 321, offering 55 hours of power reserve and viewable through a display back. Water resistance is rated at 50 metres.