Speedmaster 57' Chronograph 38.6 mm – The 1957 Trilogy Speedmaster '57 Omega Co-Axial Chronograph 41.5 mm Speedmaster '57 Omega Co-Axial Chronograph 41.5 mm Speedmaster '57 Omega Co-Axial Chronograph 41.5 mm Speedmaster '57 Omega Co-Axial Chronograph 41.5 mm Speedmaster Mark II Co-Axial Chronograph 42.4 x 46.2 mm Speedmaster Mark II Co-Axial Chronograph 42.4 x 46.2 mm Speedmaster Mark II Co-Axial Chronograph 42.4 x 46.2 mm