The Vintage Wrist Watch Company has dated this piece to the 1910s.
Cortébert registered the Jupiter name in 1913 so this ties up nicely with the movement identification.

The watch measures 35mm diameter excluding the winding crown and the articulated lugs. The case is silver and there are hallmarks for .935 silver inside both of the case backs. The case is in good condition just some unevenness to the back but overall very acceptable for a watch from the WW1 era.

The glass lens is in good condition.
The signed dial has a small amount of damage by number 2 but you have to look closely to see it. Original hands, a subsidiary seconds dial and an outer minute track.
A new leather strap has been fitted.
The watch will be sent in a new presentation box.
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The Vintage Wrist Watch Company has dated this piece to the 1910s.
Specialists in antique and vintage wrist watches and pocket watches
You can view the stock and full dealer information on the The Vintage Wrist Watch Company Profile Page