The value of your coin collection will be based in part on how rare your coins are. If your coin has an error, this is one characteristic that will make your coin rarer and more valuable than it would otherwise be. Therefore, you will need to know how to look for these types of coins.
Inspecting Your Coins
You may have an error coin that you are not even aware of. Place your coins on a table, flip them so the heads are facing up and organize them by type. Inspect the coins to determine if there are any differences among them other than wear-and-tear, the state or the date. Then, flip the coins over to look at the tails. Using a magnifying glass may help you notice small mistakes. If you are not sure if the coin is different, try looking at it from varying angles.
What to Look For
Look at the letters to determine if a portion of a letter is missing. Dirt or grease on the die face while the coin was being manufactured can cause the die face to not strike the coin properly. There might also be a doubling of the letter or some other abnormality. Next, check the portrait on the coin to determine if there are any missing elements. Look at the eyes, ears, mouth and chin.
The orientation of the top and bottom of the coin can cause the coin to be very valuable. Flip the coin and determine if the orientation changes or not. If it does, you will have a coin that managed to make its way into circulation despite efforts by mints to prevent this.
Examples of Famous Defects
Starting in 1980, the coins in Philadelphia had a "P" placed over the date. However, in 1982, there was an error that caused a small number of coins to be circulated that do not have the "P."
Another very rare coin is the 1944 steel cent. Leftover steel blanks were stamped accidentally, which were then coated with zinc. The penny will feel like it weighs less, and it will also attach to a magnet.
Hopefully the Defect is Noticeable
Even if you find a unique error, the mistake will need to be noticeable. If the coin only has a small error, the value of your coin will not be likely to be higher. While a magnifying glass can help, those coins that are clearly defective to the naked eye are the most valuable.
For more information, click here for coin dealers online or do an online search.