What makes it a chronograph ?
The primary feature of a chronograph is the ability to record elapsed time so all of them much have a built in stop watch technically. Although some could also include the features of a dive watch they would still be classified as such however, with a chronograph feature. Most commonly, but not always, a chronograph will features a tachymeter use to measure speed and distance. Another feature is the number of sub-dials on a chronograph used to measure hours, minutes, seconds and even tenths of a second.
