This link is a decade old, but still fun. The Antique Roadshow’s website has a section titled ‘Tips of the Trade‘ where different appraisers give tips that help them in deciding appropriate values. One of the tips is Searching out maps which talks about the different things that help them appraise the value of a map that they are brought.
Little statements such “Maps that show incorrect information—such as this non-existent lake—are sought after.” pepper the article.
Fun stuff I say! Now, go check it out.