There is no standard, despite endless threads and discussions on every watch forum I have ever visited. That's actually a good thing IMO, as "vintage" then becomes a matter of personal preference. And I prefer what I prefer.
Personally, I'd include 80's pieces now. I'm not looking forward to the time I include 90's in the vintage bracket!
I thought thirty years was the 'vintage' horizon. Any time interval is pretty arbitrary. I would go with pre-quartz in this case - anything from the period when mechanical watches were the standard product for timekeeping.
It's a bit like that saying about the difference between art and pornography, I know it when I see it
As a rule of thumb, anything older than Dennis is Full vintage. Then, there is pre-vintage, near vintage, classic, and "used"