How do I verify that my print/map is authentic?
Most items that we offer for sale can be authenticated by reference to their physical characteristics. Different printing methods produce prints with differing physical characteristics. It is not possible to replicate all these physical characteristics using modern planographic printing methods.
Engraving was the most common printing method in 19th century books and newspapers. Engravings are very labour-intensive to produce, and this printing method was largely replaced as the main method of commercial printing by offset lithography within a decade or so of the invention of the latter around 1890. Engraved prints bear characteristic features of engraving which cannot be replicated with modern planographic printing or copying methods. A wood engraved print is created from a wooden block which is carved or engraved before being inked and applied to a page under pressure. The pressure produces small ridges on the page, and the act of the pressure causes the ink to try to escape from the raised parts of the block. This results in characteristic ink patterns around the main printed part of the page. Both the ridges and the small ink patterns can be seen under a strong magnifying glass or linen tester at 10x magnification or above; sometimes the ridges caused by the pressure can be seen with the naked eye. The pressure also sometimes forces small spots of ink through the page, appearing as dots on the reverse side of the page. The ridges caused by pressure exerted by printing the text on the reverse side of the page are often particularly noticeable upon close inspection.
The use of a plate or block applied under pressure to the page often result in a rectangular impression left by the plate (the plate mark) around the outside of the print, although this will not be the case where the plate is larger than the page itself.