"Rare", "Numbers matching", "original", and "unmolested" are a few of the words that will indicate that the seller is looking for top dollar for the car, and are usually indicators to me to keep looking.
I don't want a "rare" or "numbers matching" car. I want something that I can enjoy, do with as I please, and not have to worry about each and every time I pull the damned thing out of the garage.
Maybe I'm not a purest when it comes to the hobby, but geez, man, I want to enjoy the hobby, not live for it.