"1943 Penny
In recent years a "1943 S" (San Francisco Mint) copper coin has gone for about $60,000 dollars at auction. I remember the prices from the P (Philadelphia) mint ranging from around $10,000 many years ago to $73,000 in recent times. There are many counterfeits of this coin. Source
The easiest way to determine if a 1943 one cent is made of steel, and not copper, is to use a magnet. If it sticks to the magnet, it is not copper and is worth about 50 cents. If it does not stick, the coin might be of copper and should be authenticated by an expert. Source
Only forty 1943 copper-alloy cents are known to remain in existence. Coin experts speculate that they were struck by accident when copper-alloy 1-cent blanks remained in the press hopper when production began on the new steel pennies. Source"