I am indebted to Peter Stubbs for much of the information below (extracted from Peter's site and his permission for allowing me to use this on the Harberton website.
The reverse of the card is smooth, like earlier postcards.The rag content in the card stock allowed a much more colorful and vibrant image to be printed than the earlier "white border" style.Charlton of Philadelphia, who patented a postal card, and sold the rights to Hymen Lipman, whose postcards, complete with a decorated border, were labeled "Lipman's postal card". In Britain, postcards without images were issued by the Post Office in 1870, and were printed with a stamp as part of the design, which was included in the price of purchase. The larger size was found to be slightly too large for ease of handling, and was soon withdrawn in favour of cards 13mm (½ inch) shorter.The first known printed picture postcard, with an image on one side, was created in France in 1870 at Camp Conlie by Léon Besnardeau (1829–1914). The first advertising card appeared in 1872 in Great Britain and the first German card appeared in 1874.The first postcard to be printed as a souvenir in the United States was created in 1893 to advertise the World's Columbian Exposition in Chicago.
The Post Office was the only establishment allowed to print postcards, and it held its monopoly until May 19, 1898, when Congress passed the Private Mailing Card Act, which allowed private publishers and printers to produce postcards.Despite the name, linen postcards were not produced on a linen fabric, but used newer printing processes that used an inexpensive card stock with a high rag content, and were then finished with a pattern which resembled linen.The face of the cards is distinguished by a textured cloth appearance which makes them easily recognizable.The world's oldest postcard was sent in 1840 to the writer Theodore Hook from Fulham in London, England.The study and collecting of postcards is termed deltiology.Stamp collectors distinguish between postcards (which require a stamp) and postal cards (which have the postage pre-printed on them).