I'm a newcomer to marble collecting and my knowledge is very limited. Marbles in my youth (70's UK) were pretty much always Chinese made cat's-eyes.
I soon realised that the shipping costs from the US to the UK for a single marble weren't significantly different to shipping a packet. Then the doubts started...
Some of the packets sold on ebay didn't look right even to my untrained eyes, and other members confirmed it. The more I looked, the more I realised there were more bags of marbles that didn't look right than did. Whilst I'm sure many of them are sold in good faith by people who've picked them up somewhere not realising the bags are fakes, fantasy or more kindly reproductions possibly some are sold to deceive. I won't make that judgement call, just whether what is listed is what it purports to be.
Hopefully this thread will be useful or at least an interesting perspective to other newcomers.
Please do chip in with thoughts.