Quarter
From Halopedia, the Halo wiki
A Quarter is an ancient coin used by the 20th-21st Century US government as part of its national currency. Equivalent to 25 Cents, under the United Earth Government the currency was discontinued in favor of the UN Credit[1], and Quarters have become valuable antiques, but have no value as currency anymore.
One side of a Quarter bears an image of ancient US general and president George Washington, while the other side bears an Eagle, the national symbol of the US. Dr. Elizabeth Catherine Halsey brought one with her while testing John-117, a potential candidate for the Spartan II Program, flipping it to test whether he could accurately predict the outcome. As a reward for guessing correctly, she allowed him to keep the coin, and the eagle became the symbol for the Spartan II's.
