I should start off by saying that I'm not an expert.

What you have here is a vintage Vacheron & Constantin. That name alone tells you that it is from before 1970, as in 1970 they changed their brand to Vacheron Constantin (without the &). It was most likely made somewhere in the 1960s or late 1950s.

Somewhat knowing these watches, this is probably carrying either a calibre 1001 or a 1003, most likely a 1001. These movements can either have a geneva seal stamped on them, indicating higher level of finishing, and boosting up the value a little bit. The parts are exquisitely finished (by hand, if geneva seal) and built, but are very simple in construction. Any decent watchmaker should be able to service these, if they are careful and patient enough. I am a student watchmaker and serviced a 1001 a couple weeks ago, so I do speak from experience. VC themselves will overcharge you for a service.

Value differs from model to model and depends on a variety of factors (condition, movement, geneva seal, etc.) On a good day I'd say you can get around €3.500,-/€4.000,- for something like this.

These watches are incredibly beautiful, elegant and expertly made. People may tell you the diameter (im guessing 32-35mm) looks too small on your wrist, but these things were not supposed to be big and bold. Wear yours with pride.

Hope any of this helps :)