But novices shouldn't expect to fly into London, scout around the shops and pick up a few maps that can be resold for enough profits to pay for the vacation. Anybody who buys a map should like the look of it and hang it on the wall to enjoy it. Even if you know where all the best shops are, it helps to know a little bit about old maps before walking in. The first maps in the general shape of the world as we know it, showing some sort of Americas, date from the time of Columbus. But the maps generally available to collectors date from the mid-1550s, when copper plates replaced woodblock engravings and maps began appearing in atlases, which are the source for more than 90 percent of the surviving antique maps.
Many factors affect the value of a map.
Most important is its rarity, followed by condition, which can change the value by as much as 30 percent. But dealers say that neither modern coloring nor partial restoration necessarily lessens a map's value. Accuracy, or rather the lack of it, often makes a map more interesting and therefore more valuable. My 1704 Dutch map, for example, is always good for a few comments or giggles from visitors, depending on what they think about seeing California as an island. Canadians love maps, some as recent as the 19th century, that show much of their country as uncharted territory, marked only by pictures of wild animals and Indians.