Beer steins--pronounced "shtines"--date back as far as 1525 in Germany. They were created as a sanitary measure directly following the outbreak of the Black Death that killed almost one third of Europe in the 14th century. The word "stein" is thought to be abridged from the German word "Steingut", which means stoneware--a material of which German beer steins are characteristically made. Another theory is that "Stein" originates from "Stein Krug", which means "stone mug".
Examine the material of the stein in question. Steins are generally made of several materials, including pewter, stone, earthenware, and wood. Wood steins are rarer, since they predate the 1800s.
Check for a hinged lid. As the introduction mentions, beer steins were created as a result of the outbreak of bubonic plague in the mid-1300's. The hinged lid was meant to maintain the cleanliness of the beverage contained in the stein.
Look for the country in which the stein was made. If it is stamped "Made in Germany", it is a strong indicator of the stein's authenticity. This was obviously not done in English, but in an old German alphabet called Fraktur Font which was phased out by the 1940s. There is a link to a character-by-character Fraktur font in the "References" section of this article.
Measure the beer stein. Traditionally, authentic German beer steins were two times as tall as they were wide--they were very tall and thin, although there are exceptions.
Check for detailed engravings. Although the earliest beer steins were not decorative, later on artists produced remarkably engraved beer steins--for example, Royal Vienna, Mettlach, and Meissen steins were all characteristically ornate. They were hand-painted and magnificently engraved.