OMEGA Speedmaster Calibre 321

The Omega Speedmaster Calibre 321, reference 311.90.42.30.99.002, is a chronograph in platinum with a 42 mm case. It measures 13.39 mm thick with a lug-to-lug of 47.6 mm, and the black dial sits under a sapphire crystal with anti-reflective treatment on both sides. The manual-winding calibre 321 movement uses a column wheel mechanism and Breguet balance-spring, finished with 18K Sedna gold PVD coating, and runs with a 55 hour power reserve. Small seconds and a tachymeter scale accompany the chronograph function. A transparent caseback shows the movement. The platinum bracelet closes with a foldover clasp, also in platinum. Water resistance sits at 50 metres.