Some have suggested that the Peruvian unit of currency, the "sol", is derived from "solidus", but the standard unit of Peruvian currency was the "real" until 1863. Throughout the Spanish world the dollar equivalent was 8 reales ("pieces of eight"), which circulated legally in the United States until 1857. In the US, the colloquial expression "two bits" for a quarter dollar, and the stock market currency "real" last used for accounting, traded in of a U.S. dollar until 2001, still echoes the legal usage in the US in the 19th century.