Antique Steins
There are 700-800 antique & vintage steins for sale on Ebay at any one time. This is a sufficiently large market that you can be sure some of the sellers have no idea what they have so there is an opportunity to profit by buying cheap. On the other hand, some of the sellers are very knowledgeable and you can learn a lot from reading their item descriptions.
My uncle, now long dead, was an avid stein collector. He lived in souther Minnesota and did his collecting in the 1980's & 1990's; before the internet. We would see his finds when we visited but didn't pay as much attention as we should have. He was a member of the Mettlach collectors group and studied all the time. Of course, he had to do it from books and by reading ads in The Antique Trader.
So, if you are trying to value a stein you own, or are looking to buy, take a look at the listings bel;ow and see if you can find something.