This map sounds pretty primitive. Now, if you want a real mystery, look up the Piri Reiss map from the middle ages that shows mountain ranges, ocean troughs and other features not discovered until the 1950s.
One odd fact about this Vinland map, though, if it is genuine, is that it would be the only clear connection between America and the Roman Empire, which gave its last gasp at the Council of Basel.
The Piri Re'is map shows what appear to be land features in Antarctica. Pretty good for a Turkish Admiral 500 years ago.
The Holy Roman Empire survived until August 1806, when Emperor Francis II laid down the emperor's crown.