I like to buy marbles or at least try to. Marbles sold on Ebay is hodge podge of truth, ignorance, and out right fraud. You might say it is the wild west, where anything goes. It is even hard for experts. With marbles you must rely mostly on photos to tell what they are. Blurry photos, marbles in containers, and far away pictures dominate most of the auctions on Ebay. Most of the sellers claim ignorance of what they are; i.e. I know nothing about marbles; I bought marble reference books and cannot tell heads or tails of what these are; or someone else told me these are old. Some sellers tell a story about their claim of authenticity like; I bought these at an Estate sale of a 200 year old man that is been collecting for years. The problem in that is that if you collect, you sometimes acquire modern marbles or maybe collect only modern marbles. Just because someone is old it does not mean what they collect is old.  Some sellers claim to be experts and tell you exactly what marbles they are selling. Watch out, this is where the fraud occurs. Many modern marbles look like old marbles. It is not that modern marble have no value, but it is that the old versions have the most value mainly from their scarcity. Acquiring some known modern marbles will greatly increase your eye for spotting old marbles. Get some modern Jabo (Vitro)'s, Mega (Vacor, Mexican made), Chinese swirls, Korean, and maybe Marble Kings. After examining these types you may be able to spot these examples in those piles of marbles that are listed on Ebay. And generally when you see a few modern examples, then usually all the rest of the marbles are probably from the same age. Yes, there are sometimes a few gems in the pile. For identification of those gems you will need to get a couple a reference books. There are also few web sites like www.marblealan.com, www.peltiermarbles.com, and www.blocksite.com that give out information and pictures about marbles. And finally just find some Ebayer sellers that sell and buy marbles and look at what they buy. Just look at their feedback from other sellers.