A real rarity!

In 1970, ESA starts to secretly develop a chronograph mechanism for the ESA 9162. It finally appeared in May 1972 and is known as the ESA 9210. Production is limited to 21,000 units.

Certina and Longines also used this movement in their watches. Below is the Omega F300 Hz Speedsonic that utilizes this ESA 9210.