How do we determine the publication date of antique maps?
Some customers like to see a date printed on a map, and we’re often asked how we know when a particular map was published if that is not the case. We’re always happy to provide a certificate of authenticity for any maps purchased, detailing the provenance of the map and our opinion of its publication date, and to let you know how we reached our opinion.
While older and individually published maps frequently do have a date printed on them, many 19th century and later atlases do not state the publication date on each individual map therein. Even where a date is printed on the map, this may be the date or year when the plate was originally engraved – it does not preclude the map having actually been printed later than that, if the publisher did not update the date stated in the plate or block at the time of printing a later edition.
If a map has been extracted directly from an atlas, dating is usually straightforward as the publication date of the atlas is almost invariably printed on the title page of the book (although publication dates of subsequent editions or impressions were occasionally not altered). If we are selling a map that we have purchased as part of a complete atlas, we usually retain the title page, and can produce a digital copy upon request. However, if we are selling an individual map that we have purchased as such, we may need to do a little research and make other checks to verify or estimate the publication date. There are several helpful indicators we can use.
The plates or blocks from which maps were made deteriorated progressively with use; initial impressions made using a particular plate are usually strong, crisp and clear, indicating an early edition, while a weaker impression lacking some fine detail might indicate a later print. Then as now, map makers needed to keep their maps up to date with events and new discoveries: changing geographical features such as railways, national borders, or revisions to coastlines reflecting recent surveys often provide important dating clues. Plates sometimes stayed in use for decades, and often changed hands between one firm of cartographic publisher and another mapmaker – publishers were usually keen to take credit for their work, and the name of the publisher was usually printed on the map, which can often conclusively narrow the range of possible publication dates. Printed text, and the content or positioning of vignettes or cartouches often changed with subsequent editions of a map. Finally, the quality or thickness of paper used may well have changed between publication of different editions or impressions, and old paper used in map making often contained a watermark which can provide an important clue as to the provenance of the map. Such changes are usually catalogued in the many thoroughly-researched cartographic reference books available to map dealers which detail the various progressive states of each important map.