Unfortunately, maps are not always in perfect condition (i.e. in the same state as when published). What are the issues to look at when considering the purchase of a map?
The regular opening, flattening out and refolding of a volume of maps in day-to-day use frequently created wear at the centerfold. As such this is not a default, as it proves that the map was an authentic part of an atlas. In more serious cases (certainly when the quality of the paper was not optimal) this may result in a tear or split, usually at the bottom of the fold. This can be repaired and there should not be any loss of print.
Certainly if you consider the map to be framed, the margins are important. The larger the margin between the dimensions of the map and those of the paper, the easier the framing and often also the more beautiful the end result will look like. One should take at least one cm as a minimum margin.
Small circular holes may have been created by bookworms. Depending on the seriousness, repairs may disguise any damage.
Many atlases and maps have, at some time, suffered from staining of some nature. This may be caused by water, tobacco, candle wax or oil. Since paper is a product of nature and because of the time factor the paper may show natural signs of browning.