It could also be a very well preserved bike and not a part bike.
I have a 79 Yamaha XS1100 that I bought with 318 miles on it. Everything on the bike is in excellent condition. Nothing seized or rusty. All nuts and bolts feel like they were just put on last week. I did replace the tires because they were hard, but the inner tubes were still soft and pliable (yes replaced those too). I runs like new.