Omega Railmaster Co-Axial Master Chronometer, Ref: 220.10.40.20.01.001, 40 MM Stainless Steel Case, Black dial with a fine linear brushed finis, Vintage colored luminous index hour maker, Screwed-in solid case back with the Seamaster Seahorse logo oriented & aligned with the watch, thanks to Omega's patented Naiad Lock system, Omega caliber 8806, beats at 25,200 vph, contains 35 Jewels & has an approximate power reserve of 55 hours, scratch resistant crystal, unworn with box and papers.