Vintage Vacheron Constantin

Hi everyone, I'm completely new to this sub, but would like to ask a question regarding this watch. This is a heritage left by my Grandfather to me, my father had it for several years but never discovered it's model or the model name, do any of you specialists know which model is this Vacheron left by my granpa?

There aren't any Vacheron stores close to where I live (Northeast Brazil) so I can't verify on it. If anyone knows the model would be of great help. I hope to sell it later once I find the model and get a new certificate of authenticity to it.

Thanks!