In 1970, ESA started to secretly develop a chronograph mechanism for their ESA 9162 tuning fork movement — the latter being used in many watches of the period including Omega f300s, Longines Ultronics, Baume and Mercia Tronosonics, Tissot Tissonics etc.  

ESA sub-contracted the design and manufacture of this chronograph module to Dubois-Depraz — this company specializes in making bolt-on chronograph modules for the major watch manufacturers and are still around today. A good read can be had here and on their website here —> http://www.dubois-depraz.ch/

It finally appeared in May 1972 and is known as the ESA 9210. Production was limited to 21,000 units. Omega, Certina, Longines, Baume & Mercier, Derby and a few others used this movement in their watches.  Like the other manufacturers, Omega assigned their own calibre number to the ESA 9210 — the Omega 1255 and the Omega models that used this new calibre were part of the Omega f300 Speedsonic range.

I’ve written a couple of other pages that are very relevant to the Omega f300 Speedsonic:

• ESA 9210 Tuning Fork Chronograph Movement
• Building two new-old-stock Omega f300 Speedsonics

Cases

The two Omega case numbers used in the Speedsonic range are:

• 188.0001 : this is the famous “Lobster” case (with Lobster bracelet) and only came in stainless steel
• 188.0002 : the more conventional case which came in stainless steel or gold plate

 

Dials and Hands

The photos below show the dial variations for the 188.0002 cases. The grey and blue ones are found in the stainless steel case while the brown and gold ones are found in the gold plated case.  Aside from the colour, the main difference is that the hour markers are either printed lume markers or applied raised markers.

The dial for the 188.0001 Speedsonic Lobster case is black mirror dial — photo to follow!

I’ll be adding information on the hands as soon as the photography is done.

Gallery

Below is a selection of photographs of stainless steel and gold plated cased Omega f300 Speedsonics with case 188.0002; some have lumed hour markers while others have raised batons.