I am new to colleting coins and in looking through some coins I found a 2002 dime that seems to have a smaller head on it. There seems to be more blank space than on other dimes that I have compared. Is this a unique mistake?
First of all, welcome to Cointalk. Second of all, you are going to have to post a picture. If I don't say it, someone else will beat me to it.
What you have there is a proof dime. They are minted for collectors...that is why the fields have a mirror look to them and all the devices have a white frosted look to them. The head is the same size on this dime as it is on any other dime...but the quality of the strike is better because of the process used to make a proof. That and the contrast between the frosted devices and the mirror field might be making the head appear smaller to you.
Then in all likelihood it would be a counterfeit. Just looking at the photo of the coin...in my opinion it looks normal. Because the coin is in a flip...I assume you bought it rather than finding it in circulation. Do you know if this is a silver proof or a normal proof? The easiest way to tell is by the rim. If you see a copper color on the rim it's a normal proof...if you do not it's probably (although not guaranteed) a silver proof. Also, welcome to Coin Talk!
Numismedia lists a 2002 S Clad Deep Cameo at .52 cents in PR60 condition. But your's might be a higher grade, although I am not experienced enough to tell. If you click on the link it shows you the prices for the higher grades.