Colouring
An antique map with gorgeous original color will generally sell for more than an uncolored example, a recently colored example or a poorly colored example of the same map. By contrast, if the same map is poorly colored or the old color has caused damage or has offset (transferred onto the opposite side of the map from having been folded into an atlas), the value of an uncolored or recently colored example will fetch a higher price.

In between these two extremes, the difference is largely a matter of personal preference. Very few collectors are actively seeking uncolored examples of maps by Ortelius, Blaeu, Hondius and other mapmakers from the Golden Age of Dutch Cartography, yet over half of all the maps and atlases issued by these makers were offered uncolored. As a result, over time, when these uncolored maps were offered for sale by dealers, many had them colored. Some dealers will refresh old color, especially if the map requires minor repairs or cleaning before the map is sold.

All reputable dealers can distinguish between old and modern color in almost all cases and they note if a map is in original or recent colours. The last issue point on color is whether the color is correct. Poor color can reduce the value of a map by 50% to 75%.
 

Certain maps were not colored at the time of publication. Most editions of  Robert Dudley's sea charts and Vincenzo Coronelli's maps are examples of maps which were usually not issued in color. Most collectors looking for these maps expect to buy them without color and would find modern colored examples less valuable than uncolored examples.

Several already in their days well respected colorists did exist. The most well know colorist was Dirk Jansz. Van Santen, who coloured the well known Atlas Vander Hem. Other colorists are Koerten, Anna Beek. Many of them used lavishly gold and silver to highlight titles and cartouches.

As to whether color or black and white looks better (or is worth more), that is a personal preference.

Select coloring 

Paper
The art of paper making evolved significantly between the time of the first printed map and modern times. Until the early 19th Century, most maps were printed on hand made paper. Early paper was made by combining the pulp from rags with a liquid formula, spreading the wet pulp over chains and laying the pulp out to dry.
Watermarks on the paper can be helpful in dating--but often mapmaking houses laid in huge stocks of paper and kept producing maps from particular batches for up to 40 or 50 years at a stretch

By the late 18th Century, there were widely varying degrees of paper quality. The quality of paper used for certain cheap mass produced British "Magazine" maps is very different from the thick high quality paper which was used by the top London / Amsterdam mapmakers. Certain late 18th Century French mapmakers used a paper with a blue-green hue. 
Beginning in the early 19th Century, machine made paper was becoming more prevalent and the content of the paper was evolving away from rag and cloth. By the mid-19th Century, cheaper machine made paper was employed by some publishers and during this period and through the end of the 19th Century, some maps are characterized by a brittle quality, caused by a higher acidic content in the paper.

Damage to Paper:
 Water stained
 Foxing and or soiling in Margins
 Foxing and or soiling Printed Image
 Margins Trimmed
 Worm Holes
 Loss of Printed Image
 Discolouration of center fold due to glue used on binding slip
 Offseting due to color oxidation
 Paper broken on places due to green oxidation
 Tear(s) in Margin
 Tear(s) in Printed Image
 Fold Split in Margin
 Fold Split in Printed Image

Margins: --Select margins--  Usual margins  Large margins  Cropped margins;

Folds & Centerfolds
Most antique maps come from either books or atlases, and therefore have been folded at least once. If the map is from an atlas, it normally would have been bound into the book using a strip of paper (a guard), which was sewn into the binding, with the map in turn glued to the guard, so that the map can be viewed flat and the centerfold is not tightly bound into the book and inaccessible. 

  --Select splits and folds--  No tears or splits Marginal split in lower or upper center fold A few very minor marginal tears Split in lower or upper center fold running until 1 cm into engraved area. Split in lower or upper center fold running until 3 cm into engraved area. Split in lower or upper center fold running until 10 cm into engraved area. Split lower or upper half center fold. Split of complete centerfold

Plate Marks.
The earliest printed maps were printed using either wood blocks or copper plate engraving methods. By the middle of the 16th Century, the use of wood blocks was being phased out, and copper plates were the prevalent method for the next 300 years. At the end of the 18th Century and first part of the 19th Century, several new printing methods were invented, including the use of steel plates, lithography, and cerography. By the middle of the 19th Century, copper plates had largely been replaced by lithographic printing methods, which remained the primary method for making maps until the latter part of the 19th Century, when new mass production methods replaced lithography.

The earlier methods of map printing are characterized by plate marks, showing the impression the printing plate or wood block left on the paper when the map was printed. This compression mark typically appears outside of the neat line on the map. For earlier maps (wood blocks and earlier copper plate maps), the plate mark is generally 5mm. outside the neat line. Many reproductions of early maps can be readily identified by either the lack of a plate mark or a plate mark that is too far from the neatline.

From the earliest times, maps bound into books often included text on the reverse side (verso) of the map. While some of the earliest maps and views were bound into a book to be folded out, many are single or double pages, with text on the back (verso) of the map. Maps published at the end of the 16th century by Ortelius, Mercator, Speed, Braun & Hogenberg and maps published in the 17th century by Blaeu, Hondius, Jansson and many other early printers generally have text on the back of the map. 

Generally, the lack of text on the verso of the same maps is a good indicator that a map is a reproduction (although there are examples of each of these map makers maps without text on the verso and are either early proof states or later reprints).

Image / Imprint
If the impression is strong and clear, the map could be from an early edition; a weak impression probably would indicate the opposite.

  --Select imprint--  Dark impression Normal / avarage impression Weak impression

Repairs 
Minor repairs of a flaws, a small tear, a wormhole, minor staining or foxing, a narrow margin, or some other imperfection to antique maps are becoming increasingly common. 

Rarity

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 * If you use this page to grade your own map note that this is not an Appraisal service and the printed valuation report can not be used for insurance, tax and estate purposes.
If you want to have a professional map dealer evaluate and grade your map according to the HiBCoR guidance please contact HiBCoR