The French engraving isn't appropriate for a British Hydrographic Service (H.S.) watch, as well as Vacheron without Constantin :-( Also hands are wrong. This one will have a place in my
Fakes and Frankens folder!
To be sure, V&C did supply watches to the French Navy, marked Marine Service Hydrographique, but they were offered through Jaeger and marked on the dial as such. Movements were marked Vacheron & Constantin. Here is one that sold at auction and, on our theme, has a 21 ligne Chronometre Royal movement.

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This Service Hydrographique chronometer also has a V&C movement. Ironically, the caliber was developed from a Jaeger LeCoultre ebauche, but the
state of wind indicator was entirely a V&C innovation. Alas, sorry for sending this thread off on another tangent...

Antiquorum photo