Here is my "Olympic" ratrappante (=split second) watch. It can be used like a pocket watch as it shows "normal time indication" with hour and minute hand and a sunk sub dial for the constant seconds "at six".
Besides this it can be used as a split second stop watch with 1/10 sec timing. These watches most probably have been used as official timers at olympic games.

The crystal is made of a special non-reflective glass, the case is covered with a special dark gray "shrink" laquer which gives the watch a very unique look.

The movement is chronometer grade and is a beauty to behold. As far as I recall it is a reserved Lemania base caliber modified by Omega.
I fully agree with Bill concerning the undervalue of theese beautiful beasts. They are not very well known among the Omega community due to their rare occurrence and most collectors ignore them as they mainly collect wrist watches. But if you are collecting Omega chronometres they are "a must" ...
Enjoy the pics and HAGWE
Erich