Precious metals (gold, silver, and copper) were once real money, and when the "shiit hits the fan" and the dollar drops off into oblivion, precious metals might be the only way to purchase from people again. People used to buy with gold and give change in silver and copper. The US discontinued the $20 gold piece in 1932, and real silver coins were discontinued in 1965, and real copper pennies were discontinued in 1982.