Back in '77 I bought a Schwinn Spitfire, and set it up with a larger rear sprocket, tire liners, thorn proof tubes, and a front brake. I did this specifically so I could use it for slamming down the dirt roads out in the hills near where I live. I discovered this little rush all on my own. Truth of it is- when I started doing this I was having so much fun that I tried to get anyone who would give me five minutes of time to come out and ride the hills. All I got was rolled eyes, and "yeah, sure" comments. Didn't stop me from having fun, and all the places I used to ride alone are now jammed with spandex boys on $1500. superbikes. Does that make me a "pioneer mountain biker?", or my old Schwinn an "early" mountain bike, or klunker?"
That there is a "vintage" market for bikes like this is just one click beyond my comprehension. So it's an old mountain bike. So what? To my eye there is just no unique beauty, no unique style, and nothing particularly desirable in 99.99% of any diamond frame bikes. I could make an exception for a hand crafted racer, or something built back in the days when all bikes were hand crafted, but aesthetically, there is nothing that separates this bike from any $50. two wheeler bought at your local discount store. Classic bikes are classic because they are works of industrial art as much as they are vehicles.
Sorry if I sound a little curmudgeonly, but I think the whole concept of "classic" bikes has been stretched way past the bounds.
JWM