Posted By:
Frank WakefieldDennis, you need to get a copy of Mr. Lipset's Encyclopedia of Baseball Cards, vol 3. It was first published in 3 volumes over time. It is now offered in a reprinted combination of one book. Mr. Lipset is on eBay and has one listed now, item # 8770956266.
That book will clue you in as to the tough ones. It is an old, dated, and yet invaluable collecting tool.