This is the sole reference that describes the various die progression states of the 1921 S Thorn Head Morgan silver dollar variety. It was written by Leroy C. Van Allen, often referred to as the father of Morgan silver dollars with his "Comprehensive Catalog and Encyclopedia of Morgan & Peace Silver Dollars". I was edited by Michael S. Fey, Ph.D., former Governor of the not-for-profit American Numismatic Association (ANA) and Senior Instructor for "Collecting and Investing in Morgan Silver Dollars at the ANA Summer Seminar. The book has numerous descriptions and photos allowing the reader to identify which VAM variety his Thorn Head represents, as well as its rarity. The price for some varieties can command thousands of dollars in the numismatic market.