OSE (Οργανισμός Σιδηροδρόμων Ελλάδος), while primarily known as the Hellenic Railways Organisation, also functioned as a mobile network operator in Greece. Assigned Mobile Country Code (MCC) 202, identifying Greece, and Mobile Network Code (MNC) 04, OSE provided mobile communication services, likely aimed at supporting its operational needs and potentially offering limited commercial services. This is a fairly unique situation, as railway companies rarely also act as public mobile operators. Other prominent mobile operators in Greece include Cosmote, Vodafone Greece, and WIND Hellas, each with their own distinct MCC and MNC combinations and wider market reach. Though details on OSE's mobile network operations are sparse compared to larger commercial providers. the use of MCC 202 and MNC 04 confirms its existence as a registered network within the Greek telecommunications landscape. The extent of its coverage area and available service types are points of interest for researchers and mobile network enthusiasts tracking the evolution of telecommunications infrastructure within Europe. It's possible OSE leveraged its existing infrastructure along railway lines to deploy its network, and further community input is greatly appreciated to expand on this initial overview.