First off, before you have anyone buy your penny, it is going to have to be certified by a third party grading company such as NGC or PCGS. They will grade the coin on a scale from 1 being very poor, to 70 being absolute perfection. They also will note if you do have a genuine 1955 doubled die cent. This costs about $50 or so, and most coin dealers can help you with the submission process. Once you have the coin certified, there are a few options. One is to sell the coin online on an auction site like eBay, another is to go to a coin show and see if any dealers there want to buy it, and the final major option is to have an auction house auction it off for you.
if its a1955 Double Die Penny$300 - $25,000+
The easy way to see one is, type in 1955 Double Die on your browser and click images.
$500-$1500
Please see the Related Questions for more information
it is worth up to $1,500 in circulated grades
The 1955 Doubled Die cent is a die variety that occurred during production of the Lincoln cent at the Philadelphia Mint in 1955.
There's a picture at the Related Link.
If the coin is double-struck, it can be worth up to $30,000. So if you see double, hold onto it!
If it's a true hub double retail values are $920.00-$2,100.00 for a circulated coin.
A circulated example of a genuine 1955 Double-Die Lincoln coin runs from $975.00 to $2,500.00
Mint error coin that has become famous in coin collection circles.
It is a common date, worth from 3 to 25 cents depending on condition.