The Omega Seamaster Planet Ocean 600M GMT 215.30.44.22.01.001 brings the Master Chronometer-certified GMT complication into Omega's most credentialed dive watch architecture, with a 43.5mm stainless steel case rated to 600 meters of water resistance and the distinctive black-and-white bezel that earned the configuration its "Oreo" nickname among collectors. The Planet Ocean lineage launched in 2005 as Omega's purpose-built 600-meter dive watch, designed to sit above the standard Seamaster Diver 300M in both depth rating and case proportions, and the Master Chronometer generation introduced the in-house Caliber 8906 with its METAS-certified antimagnetic resistance to 15,000 gauss and 60-hour power reserve. The 43.5mm steel case carries the screw-down crown, the helium escape valve at 10 o'clock, and the broad uni-directional rotating ceramic bezel split between black and white segments with a luminous 24-hour scale that supports the orange-tipped GMT hand against the home time. The black ceramic dial features applied luminous indices, broad luminous hands, and the date aperture at 6 o'clock, set behind a domed glareproofed sapphire crystal. Powered by the Omega Master Chronometer Caliber 8906 self-winding movement, with twin barrels mounted in series, silicon balance spring, and antimagnetic resistance beyond 15,000 gauss. Pre-owned, 2025 production.