Deltiology (from Greek , , diminutive of , , "writing tablet, letter"; and , ) is the study and collection of postcards. The word was first coined by Professor Randall Rhoades of Ashland, Ohio, in 1945. However, it took about twenty years for it to first appear in a dictionary. Compared to philately, the identification of a postcard's place and time of production can often be an impossible task because postcards, unlike stamps, are produced in a decentralised, unregulated manner. For this reason, some collectors choose to limit their acquisitions to cards by specific artists and publishers, or by time and location. History Deltiology appeared at the end of the 19th century, when the mass production of postcards began and received international distribution as the cheapest type of postal items. The first postcard was published in 1869, and by 1875, 231.5 million open letters were sent in the member countries of the Universal Postal Union. In the late 19th to early 20th centuries the first organizations of deltiologists appeared. Special magazines and catalogs began to be published (in Germany, Austria-Hungary, France, Russia, Great Britain, the United States, Italy, Switzerland, Spain, etc.), international exhibitions took place (in Leipzig, Saint Petersburg, Nice, Paris, Florence, Nuremberg, London, etc.), congresses of collectors and postcard publishers (in Leipzig - 1896, 1910; in Nice - 1899), the first auctions began to be held. Since the beginning of the 20th century deltiology has become one of the most popular types of collecting facilitated by the mass production of postcards of diverse topics (geography, ethnography, history, various types of art, technology, sports, portraits, etc.) and of high-quality art and printings, and by postal exchange between countries which expanded significantly with the strengthening of international relations. The initial views on deltiology were somewhat different from the ones we have today. At the beginning of the 20th century, it was believed that only a postcard that had been mailed, and thus “fulfilled its function”, could be a worthy collectible. Moreover, many collectors would only be interested in a postcard with a view of a city or locality if it had been mailed from that city or locality. A blank postcard without a postmark was equated to a simple “picture”. Today, however, some collectors actually ignore cards with writing on them. Deltiology is one of the most popular types of collecting. Postcards are usually valued in proportion to their age and