Launched in 1959, the Explorer 6610 replaced the reference 6150 and was only produced for about 5 years. Characterised by its flater caseback due to the introduction of the new caliber 1030, the 6610 is recognisable by its gilt chapter ring as well as its officially certified chronometer dial (OCC) that would later be replaced by the 1016 gilt dial with its superlative chronometer officially certified dial. Preserved in excellent overall condition, with its original dial and central white seconds hands reacting to the Geiger counter, a desirable version of the history of early Explorers.