First apologies for confusion over on WRUW thread. I have so many pictures of Index Mobile prior to buying this one - I 'screwed' up - Sorry
This watch came from the estate of George Dubey - It was owned by the person he left it too - The (at that time) present owner of Dubey and Schaldenbrand. She and George Dubey were lifelong friends.
It is a 1946/50 Champagne Face - Index Mobile made by George Dubey
The movement is a Landeron, with screw balance wheel
Split-Second Chronographs of the 1940s and 1950s
Before one examines the Index Mobile chronographs produced by Dubey & Schaldenbrand, it is worthwhile to describe -- briefly -- the operation of split-second chronographs and the state of the art, as it stood in the 1940's, before the development of the Index Mobile.
A split-second chronograph employs two chronograph second hands, which run together for a while, with the upper hand appearing to be superimposed on the lower hand. When the user wants to check an interval time, he presses a button, and that's when the magic happens -- one of the second hands stops (to mark the interval time) and the other hand continues to run. After a reading or interval measurement has been made, the user presses the button again, and the hand that had been stopped catches up with the hand that has been running continuously, and once again, they appear to be running together, as a single hand. [This "catching up" is where we get the term, "Rattrapante", from the French word, "rattrape", meaning "to catch up.] Such split-second chronographs are also called "double chronographs", or "Fly-Back Hand"
Split-second chronographs are very complicated, with a separate castle wheel and numerous other parts being required for the amazing task of stopping one second hand (while another continues) and then having the stopped second hand catch up and continue on, with the primary second hand. In addition to the additional castle wheel and additional second hand, the movement of a traditional split-second chronograph will include a split-second brake (which looks like pincers), a split-second wheel, a heart-shaped reset piece, and various additional springs and cams.
The Index Mobile -- 'The' Rattrapante
Seeing the usefulness of split second chronographs, but the issues associated with existing designs, George Dubey set out to develop a split-second chronograph that would be simpler in design and less expensive in production. Beginning with a standard Landeron or Venus movement, George Dubey created a split-second chronograph by adding an additional chronograph second hand, and connecting the two second hands with a hairspring, with the hairspring fully visible between the dial and the crystal. When the chronograph is started, both the second hands move together. The user stops the split-second (or index) hand by pushing the button in the center of the crown, which applies a brake to the wheel turning the hand. When this button is released, this second hand (which had been stopped) "catches up" with the other second hand, which has continued running throughout the period being timed.
The Index Mobile was thought of as a simple, elegant solution, to a complex horological problem -- it allowed an inexpensive Landeron or Venus movement to be modified for split-second timing. The "Index Mobile" system was a clever approach for the production of a split second chronograph. By adding a few parts, common movements were able to deliver economical, reliable split-second timing.
Acknowledgements: Mme Cinette Robert, Jeff Stein
Pictures - taken to day:
The Movement - Notice NO shock protection:
Here you can see the 'RATTRAPANTE' - Splits Second Hand.
Mme Cinette Robert
APOLOGIES to ALL