Beer Stein Library
This site has a huge amount of free, publicly available, and incredibly specific information about all aspects of beer stein history and collecting. Hint: click on the blue dots to access the links. There are exhaustive explanations, for example, of varieties of steins including figural, pre-1850, post WWII, glass, Mettlach, medal, modern, military, and more. It could take a very long time to go through all this knowledge—maybe you'd better pour a beer for your session!