Silver, in the form of electrum (a gold-silver alloy), was coined to produce money around 700 BC by the Lydians. Later, silver was refined and coined in its pure form. Many nations used silver as the basic unit of monetary value. In the modern world, silver bullion has the ISO currency code XAG. The name of the pound sterling (£) reflects the fact it originally represented the value of one troy pound of sterling silver; other historical currencies, such as the French livre, have similar etymologies. During the 19th century, the bimetallism that prevailed in most countries was undermined by the discovery of large deposits of silver in the Americas; fearing a sharp decrease in the value of silver and thus the currency, most states switched to a gold standard by 1900. In the Spanish language, Plata means both silver and money.
The 20th century saw a gradual movement to fiat currency, with most of the world monetary system losing its link to precious metals after Richard Nixon took the United States dollar off the gold standard in 1971; the last currency backed by gold was the Swiss franc, which became a pure fiat currency on 1 May 2000. During this same period, silver gradually ceased to be used in circulating coins; the United States minted its last circulating silver coin in 1969.
Note: Only 2,934,631 of 1969 Kennedy halves were minted. On 3 March 2012 they were worth about about $8 each. Read more:
The above image is of the Roman Republic Roma JANUS ROMA TROPHY Silver Coin 119BC that sold on eBay for US $575.00 on on Apr 17, 2011