bars made out of 99.5% to 99.99% pure gold which can be traded for investment purposes or held by central banks. Gold bars range in size from 400 troy ounces to as little as 1 ounce of gold; an individual can either hold on to these bars or store them in a safe deposit box. Central banks store gold bars weighing 400 troy ounces in vaults. In the United States, gold is stored at a few Federal Reserve banks and Fort Knox, for example. In the past, this gold directly backed the American currency, but now it serves more as a symbolic backing for dollars issued by the Federal Reserve.