Alexander Del Mar was a man who lived a long, long time ago. He was very interested in money and how it works. He studied and learned about money for a long time and wrote books about it. His books were very important because they helped people understand the history of money and how it has changed over time. He also talked about how people used to trade things with each other before money was invented. Alexander Del Mar was a very smart man who helped us learn more about money and where it came from.