It pays to go to church! You can search the forum for the term "fabrique pour" to get the background on this line "made for" Vacheorn & Constantin beginning in 1906. Yours was inspired by or commissioned for use during the Great War, as suggested by the utilitarian silver case and monopoussior chronograph with telemeter scale for rangefinding. The metal bracelet may be a special order as they were usually on leather strap. The obvious question is whether it was originally a wrist watch or converted from a pocket watch. The case and movement serial numbers can be submitted to VC (see Dan's post above on his lovely Fabrique Pour repeater) and their records may answer this but I do think it was always a wristie.
The movement maker may be identified if you can safely open the back and post photos. Looking at your picture of the case back, you will see the protrusion on the right of the crown. That is where a small indent exists; try pressing your thumbnail in there to open the back. If it is too tight and you are not comfortable using a case knife (or back-side of a butter knife), then take it to a local watchsmith. Please return with pictures. Nice box too .
Alex's article, The History of VC Wrist Chronographs, has pictures of Reymond Freres 13-ligne calibers from 1916 and 1927, which appear to be a match. Reymond Freres was founded in 1901 as chronograph specialists and later renamed in 1929 as Valjoux. You can see the lineage with the Valjoux 22 of the 1940s that many brands used extensively.
Reymond Freres 13-ligne caliber from 1916
Yours circa 1917
Valjoux 22 of 1940
The five digit serial visible inside the case back on your watch is likely Reymond Frere's or their casemaker. The actual V&C number is just visible on the back outside, at the bottom. I cannot make it out, but that is the number you will need to supply to VC for a record's check.