The 1943 steel penny is composed of a steel core with a very thin outer layer of zinc. A very small handful of copper-based pennies were minted during 1943 as a result of an error at the mint. According to the U.S. Mint, about 40 of these coins are still in existence and have sold for as much as $82,500 at auction. Because of their value, 1943 copper pennies have been counterfeited. To determine whether your coin is steel or copper, you can test it with a few common items.
Examine the overall color of the 1943 penny. If it is a silvery gray color, it is probably a steel penny. If it looks more like a common brownish penny, it may be one of the rare copper 1943 pennies.
Pass a magnet over the coin. If the penny is attracted to the magnet, it is a steel cent, not copper.
Weigh the coin. Steel pennies weigh 2.7 grams, while copper pennies weigh 3.11 grams.
Examine the final digit of the date of the penny closely to make sure it was not tampered with. Compare it to the dates on other cents (especially those ending in 3). If there are any tooling marks around the number, it may be counterfeit. A magnifying glass can help with this task.
If your coin appears to be a 1943 copper penny, have it authenticated by a reputable grading service.