I chose to try to learn them the other way around. I bought large groups of correctly attributed marbles by as many different companies as I could find and studied them hands on. The two books mentioned already are also the best 2 I own for this purpose, but my Grist book has the totally wrong photos for a couple of companies which drives me mad. Popular American Marbles is worth its weight in gold no matter what some others might say about the quality of the photos.