Walter Breen was an American numismatist, known for his extensive knowledge of coins and currency. He was particularly recognized for his work on U.S. coins and his contributions to the field of coin collecting. Breen authored several influential books and articles, which helped educate collectors and enthusiasts about the history and value of various coins. In addition to his numismatic work, Breen was a controversial figure due to his personal life and legal issues. He was involved in various scandals, including allegations of child abuse, which overshadowed his contributions to numismatics. Despite this, his impact on the field remains significant, with many still referencing his research today.