The Chronostop: Omega's least remembered and most misunderstood watch.
Unlike conventional chronographs that record seconds, minutes and hours with two or three subdials, the Chronostop is designed to be used for short interval timing - less than one minute - with a central hand for seconds and a single pusher.
Omega released the Chronostop in 1966. Originally intended as part of the Seamaster collection, the Chronostop was transferred to the Geneva collection in 1967 as a cheaper chronograph watch for younger buyers.
Despite its low price, the Chronostop was a premium model. The timepiece of the watch seemed simple, but it was an extremely accurate, powerful, high quality motor, essentially a simpler version of the timepiece that powered the Speedmaster. Omega used two timepieces for its Chronostop models: the cal.920 (with a date) and the cal.865 (no date).
The cal.920 appeared in 1968 and was used for 61,000 watches.