Citation, Documentation of Sources
Q. I’m doing a research project where I analyze the currency of different countries. If I want to discuss, say, the US one-dollar bill, can I cite it directly as a document produced by the Federal Reserve, or do I need to cite an image of the bill?
A. Even if you include a detailed analysis and history, currency isn’t a document in the usual sense, and it doesn’t need to be cited. But if you include an image, give the source of the image at the end of the caption.
The caption for the above bill might read as follows (see also CMOS 3.30):
The obverse of a $1 Federal Reserve note as issued with a new design in 1963. (Watermarked image from “The Seven Denominations,” at the US Currency Education Program website.)
For guidance on reproducing images of money, see “Currency Image Use” at the website of the Bureau of Engraving and Printing (US). For European currency, the European Central Bank offers this guidance.