The value of any bike is determined by it's quality and it's exclusiveness. Being old.... adds no value, or worth.

But a rare, and finely made bicycle that can not be replaced... can have real worth. Supply and demand always determines price. The closer that said bike is to like-new original condition... the better. Damaged paint or incorrect replaced parts may distract from the best price. Re-painted frames or upgraded parts may also lower possible prices.

But is this something you want to own and enjoy.... or is this bicycle an investment? The answer to that is what determines how to restore a bike.