This post has nothing to do with the stock market, but I think it is interesting nonetheless. Prior to 1982 almost all pennies minted by the U.S. mint contained about 95% copper and 5% tin and zinc.* During mid-1982 the U.S. mint changed the metallic compisition of the pennies to about 99.2% zinc and 0.8% copper. All pennies minted since 1982 have less than 1% copper.
The reason why the composition was changed is because during the early 1980s the price of copper kept rising and the total value of the copper metal in each penny was apporoaching the one cent face value of the penny. Accordingly, if the value of copper had kept rising, the U.S. Mint would have been losing money by producing more of the 95% copper pennies.
As you are probably aware, the prices of commodities have been soaring over the past few years. The price per pound of copper was recently about $2.33. At $2.33 per pound, the value of the copper in most pre-1982 pennies is about 1.45 cents, 45% more than the face value of those pennies, as discussed in this article.
For those who can afford to do so, it might be a good idea to start hoarding any pennies you receive in change that are from before 1982. At some point in the future those pennies might be worth several cents apiece to metal refiners willing to melt them down for the copper contained within them.
At Coinflation.com, you can determine the instrinsic value of various coins in circulation over the past 100 years or so.
*1943 was the exception when steel pennies were minted to conserve copper necessary for in America's WWII efforts.