I own a lot of vintage, but I'm no expert. It looks authentic to me and I think the people you dealt with are not familiar enough with vintage to know better.
As for this bag itself, I would return to seller and find another one. The canvas on this one doesn't look that great honestly. IMO, if your plan is to get the vachetta replaced, look for one with nicer canvas.
Older canvas is not always better, it really depends. I have newer canvas that is beautiful too. It can sometimes just be a luck thing. I hope you get the result you want in the end though!
As for this bag itself, I would return to seller and find another one. The canvas on this one doesn't look that great honestly. IMO, if your plan is to get the vachetta replaced, look for one with nicer canvas.
Older canvas is not always better, it really depends. I have newer canvas that is beautiful too. It can sometimes just be a luck thing. I hope you get the result you want in the end though!