Omega 331.90.42.51.04.001 Speedmaster '57 Co-Axial Chronograph 41.5mm Mens Watch. Brushed/Satin finished titanium case with polished finished beveled edges. Titanium bracelet with brushed finished outer links, polished finished center links & edges. Brushed finished bezel with engraved & black filled Tachymeter Scale. Omega caliber 9300, beats at 28,800 vph, contains 54 Jewels & has an approximate power reserve of 60 hours - thanks to its twin barrels mounted in series.