Posted By:
RC McKenzieCards can be 'too rare'. If a card is so rare that no one knows what it is, then it has no market.
Ebay is as good a place as any to sell baseball cards, just look at that Josh Gibson price on there as an example. As far as needing a grading company's blessing to place value on a card, I don't think the companies will grade any newly discovered or uncatalogued cards.