Omega and ESA Tuning Fork movements Like many other watch manufacturers in the 1970s, Omega employed tuning fork movements in many of their watches. The ESA 9162 / ESA 9184 movements used by Omega were also designed by Max Hetzel, who had previously worked for Bulova and created the Accutron 214. There is also a chronograph version of these tuning fork movements, known as the ESA 9210 and was used in the Omega Speedsonic range of watches. The Omega watches employing these tuning fork movements were usually referred to as the �Omega F300Hz' models reflecting the frequency of the tuning fork. The non-chronograph f300s must have been produced in the tens of thousands and are often seen on a popular auction site today. Omega, like many other watch makers, allocated their own calibre numbers to these ESA movements: - Omega Calibre 1250 = ESA 9162 (date only) - Omega Calibre 1255 = ESA 9210 (chronograph day and date) - Omega Calibre 1260 = ESA 9164 (day and date)