Rolex released their first chronograph in 1937. Instead of developing their own chronograph movement they decided to buy movements from Valjoux. Their co-operation with Valjoux lasted for more than 50 years.

Introducing the Cosmograph
In 1960 Rolex resurrected their faltering chronograph line with the introduction of the Cosmograph. A Cosmograph is by definition a chronograph. However, the name Cosmograph is an Rolex invention. A Cosmograph has a tachymeter scale engraved on the bezel, whereas most chronograph had/has the tachymenter scale printed directly on the dial.