The Omega Seamaster Planet Ocean 600M Co-Axial Master Chronometer reference 215.30.40.20.04.001 represents the white-ceramic-dial chapter of the 39.5mm Planet Ocean introduced in 2019, the smaller case complementing the 42mm and 43.5mm variants that anchor the contemporary Planet Ocean line and offering the most wearable execution of Omega's flagship dive watch. The reference combines a brushed and polished stainless steel case with a unidirectional rotatable white ceramic bezel carrying an Omega Liquidmetal diving scale, framing a white ceramic dial with Arabic numerals at six, nine, and twelve, luminous silver-tone arrow-shaped hands, applied index hour markers, and a color-matched date window at three o'clock. The case construction includes a screw-down crown and helium escape valve protecting 600 meters of water resistance. Powered by the in-house Omega Caliber 8800, a Co-Axial Master Chronometer certified by METAS for accuracy and 15,000-gauss magnetic resistance, with a 55-hour power reserve at 25,200 vibrations per hour across 35 jewels. Fitted on a brushed and polished stainless steel bracelet. The 39.5mm Planet Ocean has become a favored alternative to the 42mm reference for buyers seeking a more wearable Co-Axial dive watch in Omega's modern catalog. Pre-owned condition.