As we haven't found a more precise information for the watch, we quote the info taken from Watchbrothers dot com

" 1st Generation Overseas — Powered by the spirit of travel and openness to the world

Production date 1996 to 2004

Almost 20 years after the release of the 222 Vacheron Constantin launched the Overseas, a revised direction for their sports luxe offering. Produced from 1996 to 2004 the 37mm Overseas was powered by the cal 1310 (cal 1311), a COSC certified version of the ultra-flat automatic Girard-Perregaux 3100 featuring a quickset date, 150M water resistance and hacking seconds. Also released was a smaller 35mm ‘mid-size’, 24mm ladies (Quartz & automatic) and an extremely rare left hand version made in only 3 pieces.

The design team behind the 1st generation Overseas included Dino Modolo a independent designer and Vincent Kaufmann a young in-house designer today heading the VC design team.

Following on from the time/date models a Chronograph was later introduced to the Overseas lineup in 1999.

The launch of the Overseas was deemed to be a great success and went on to lay the solid foundations of further generations of the Overseas line that are still produced today.

" There is no clear date when ‘T Swiss Made T’ first appeared on the dial. It is a common misconception that all ref. 42040 are ‘Sigma’ signed and all ref. 42042 are ‘T Swiss Made T’ signed, this is not the case, the reference change was linked to the movement upgrade. ‘Sigma’ dials have been seen on ref. 42042 models up to early 2000’s with some of the later examples also featuring Luminova.

Finally the ‘Swiss Made’ dial featured at the very end of production with Luminova permanently replacing Tritium. These dials have also been found on service replacements."

For the ref. 42040 and ref. 42050 Vacheron Constantin took the Girard Perregaux cal 3100 based ebauche, renamed as their own cal 1310 and COSC certified. The cal 1310 features a gold rotor weight, and 27 jewels. It’s automatic, has a quick-set date function, hacking seconds and a 46 hours power reserve. Total height of the ultra thin movement was around 3mm.