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Early-1970s chronographsChronographA watch function for starting, stopping and resetting an elapsed-time measurement independently of the ordinary time display. with a fixed inner and rotating outer bezelBezelThe frame surrounding the crystal at the front of a watch. acting as a slide rule, in CalibreCaliberThe designation of a watch movement, identifying its design or movement family. 12, CalibreCaliberThe designation of a watch movement, identifying its design or movement family. 15 and Valjoux 7740 versions.