Before you part with your cash for the vintage bike of your dreams, how do you know it has never in its past life been stolen or obtained unlawfully?
If it has, then the bike could be seized from you at any time, without compensation.
For old bikes, it seems difficult to establish continuity of legal ownership since day one.
The sort of problems which can occur can be seen in
http://tinyurl.com/3yjsn92Buyer beware?