After looking at Golden Age book, I see most, if not all, of the bikes presented are not "restored" in the usual sense. Cranks aren't rechromed, paint and Al bits appear unpolished. I guess if we collectors had our choice, most of us would like to find that gem of a bike that had been hermetically-sealed for fifty years. I suppose others would prefer a beat-up Bianchi ridden by Coppi to TdF victory with blood stains intact. Both are wonderful...its just a matter of luck and how much one is willing to spend whether we will individually ever acquire such treasures.
This does pose a problem, for me at least. If a relatively rare, desireable bike in good condition falls into my hands, should I resist cleaning?...polishing?..."restoring"? If a common bike, do whatever you want with it. If choice bike, probably whatever you do to it will lower its value to somebody. In the end, its greatest value hasn't changed since it received the breath of life, ride it like there's no tomorrow because one day there won't be.