There is a big marble auction set for July 18th in Ohio, featuring marbles from "The George Carter Collection". It's quite an impressive lot, especially considering it's just the first of several auctions from the collection.
They have a very nice photo gallery of the marbles up for auction. I can't recall ever having seen so many antique hand-made marbles literally piled on top of each other. I hope somebody did that very carefully and didn't just dump them out for the photo!