23.
Back to the original post, though.
If you find people are going too fast, naming cards you`ve never even seen before let alone memorised, then it might be a good idea to get hold of a complete encyclopedia listing of cards from somewhere. I don`t know which magazines carry them, Inquest maybe, but once you`ve got one copy you`ll never need another. You can also find them online, although I couldn`t tell you from the top of my head where...