It was quite easy to find the "comfort zone" in what is a C&V bike, just a few years ago.....
It was usually anything built within the 80's and older, and bikes relatively did not change that much in general appearance.
Now that we are in the new millennium, that bracket has moved over to include the 90's and bikes had moved on to include a lot of CF, Ti and aluminum, plus the disappearance of things on bikes like lugs and fork crowns and the introduction of more monocoque compisite and water formed metal designs and bikes came out in so many different forms and shspes, it is a bit harder to define that line where C&V ends and the current, modern era starts.