Additional resource for further exploration
This link from the University of California Santa Cruz University Library gives an overview of primary and secondary sources and why the distinction between them is important.
https://guides.library.ucsc.edu/primarysecondary
At the link below, the Bringing History Home Project provides information on analyzing original sources using a three-step process of observation, contextualization, and corroboration.
http://www.bringinghistoryhome.org/assets/bringinghistoryhome/socc%20analyzing%20sources.pdf
Explore the Federal Reserve Bank of San Francisco’s “Showcase of Bills” for examples of currency as a primary source.
http://www.frbsf.org/education/teacher-resources/american-currency-exhibit/showcase-of-bills