The quarter is an ancient coin once used by the United States Government as part of its national currency. Under the Unified Earth Government, the currency was discontinued in favor of the UN Credit. Quarters became valuable antiques, but with no value as currency.
Dr. Catherine Halsey acquired a quarter as an antique.
When testing John-117 for his possible inclusion in the SPARTAN-II Program in 2517, she played a game with him to see if he could determine or affect on which side the quarter would land. When John succeeded, she judged that he was very capable or lucky, and he would be a good inclusion in the program. As a prize for winning the game, she gave the quarter to John.
When John was forcibly inducted into the SPARTAN-II program, the UNSC confiscated the coin. John fought madly to get it back, but was unsuccessful.
In 2552, while in the clutches of the Gravemind, Halsey's posthuman duplicate Cortana began to relive Halsey's memories. Cortana remembered how Halsey acquired John for the SPARTAN-II program using the quarter toss as the deciding factor and because she felt guilty about it, declared his selection to be "the coin's fault."
- Even though Halo: The Fall of Reach states that quarters and all forms of material currency were discontinued, various material currency such as the quarter and dollar can be found in Halo 3: ODST.