Collecting Antique Maps - Whats on the Paper?

Should there be a crease down the middle? Well yes and no, it depends on the map.  To be fair if a person has no knowledge or experience of antique maps its unlikely they would be able to answer that question.  Most printed maps avaialble to collectors today are printed maps that were originally bound in books and atlases, hence a crease down the middle where the page was folded is very common, but not always the case. . . . 

Above: Part of a Map of England & Wales 'Anglia Regnum' Duisberg 1595 by Mercator.  Having got to grips with the paper itself, the next important step is to know what to be looking for on the paper itself. Identifying elements is what you're after. You can see the basic identifiers on a 16th century double page map here . . .  Map Identifiers 16th Century