CSA currency
Edit - It is correct that CSA paper money was sometimes referred to as graybacks (or greybacks). In fact, that is the first definition listed for that term in "The Civil War from A to Z" section of this website.
However, the question began with the word "who," indicating that the desired answer would have to be, if not a person, at least a living creature of some sort. That being the case, currency just doesn't fit.
hoosier