Trying to figure out whether a map or a print is an original or a reproduction is something that can be done by any purchaser as long as one knows what the determinants are. A trustworthy seller is also a factor in determining whether a print is an original or not. Verifying the printing process, paper and other factors may help in ascertaining the authenticity of a print or a map. Professionals in this line of business would of course be able to determine an original map or original print from reproduced ones. However there are methods on verifying its authenticity. First of all it would be good to know what an original is. An original print or map is one that is made during an artist's lifetime. It is an impression made out of blocks usually wood but could be stone or metal as well. These are then cut from the designs that the artist made himself. It is possible to have later reprinting's and still consider the print as an original so long as they are still made from the original blocks. However blocks which are recut completely may still qualify as an authentic if it was made to replace damaged or lost blocks during the artist's lifetime. A fake map or a fake print simulates the effects of age pigments and papers. This kind of reproduction is meant to deceive. In technical terms there is no vast difference between a fake and a reproduction.
The real difference however comes from the intentions of producing and selling it. Reproductions are also made from a photomechanical process which as a result would produce an image composed of many small dots. If you use a 10x magnifier this dot-matrix process would have revealed to you and you would immediately gather that you're looking at a reproduction print or a reproduction map. It is also important to discern the time period where the print or the map is supposed to come from. If, for example the print or the map that you are looking at is supposed to come from the 19th century then you need to understand that back then the most common method for printing newspapers and books was steel engraving. Thus when you recognize the time period of a particular print, the knowledge of the printing method in that century may come in handy in determining an original print from a reproduction print. You would then consider looking at the plate marks of the print, if any are to be found you may be looking at a reproduction print, especially if what you have is supposed to be a lithograph or wood engraving. A print that is wood engraved is made from a block, that of course comes from wood. This is engraved before inked. Back then they used pressure to apply this to the page. As a result, there would appear ridges that are on the page and the pressure makes the ink escape from the parts of the block that were raised. Ink patterns around the page that was printed would then have certain characteristics. You can use a magnifying glass once again to make sure but sometimes this can even be seen using the naked eye.