Our Heritage Frontier is my favorite merit badge frontier. As I have gotten older, I have fallen in love with history. As a student (even in college) I hated it. Now as a home school mom, and getting to teach history with good history books, I really enjoy it. I have learned so much teaching the kids history.
Dawn of Our Country is a great merit badge. It looks at the formation of the great county that we live in. Part of that history is the historic symbolism found in everyday objects such as our currency. Optional requirement number twelve looks at the back of a one-dollar and two-dollar bill. If you have an Explorer working on this requirement, the print-out below should help. It provides images for them to look at along with lines for them to write on so they can easily turn their work in to their unit leader.
I learned a lot about the symbols myself. There are many great resources available on line. Two that I found helpful were Wikipedia and Artlex.com
NOTE: The text of the requirements have been greatly simplified here. Please be sure to read the full text in the Girl Handbook to make sure you fully understand the requirements.