What are you referring to? Does the coin have two images of Lincoln? If so, it could be worth a few bucks at retail. If you're describing a coin that has a little picture of JFK or someone else pretending to stare at Abe, you have a novelty piece made outside of the Mint that is only worth a cent. Also, to clear up terminology, coins are said to be "struck" or "minted" rather than stamped. Not sure why; it's just always been that way.
Around $20.00 for a minor mis struck error.
The British New Penny coin was first issued in 1971.
It's worth 2 cents for the copper.
Maybe 25 cents
Average value is $1.00 for a proof 1971-S lincoln cent.
It's still worth 50 cents, the dates stamped into the coin adds nothing to the value.
It's a novelty coin that was not made at the mint and has no collectible value.
Indelibly Stamped was created in 1971-06.
I'm not sure what you mean "mixed with a penny". If the coin is made out of copper-nickel like an ordinary dime, but has a cent image struck* on top of the dime image, that's possibly a mint error that happened when a dime accidentally got mixed in with cent blanks and was struck a second time. That's definitely a collectable error but you'd have to take it for in-person appraisal to be sure. If one side is a cent and the other side is a dime, it's a fake made by joining halves of 2 genuine coins, and has no value other than as a curiosity. (*) FWIW, coins are said to be struck or minted, rather than "stamped".
If it was found in change, face value to 2 cents depending on its condition. An uncirculated one is worth a nickel.
A 1971 double struck penny, featuring two images on both sides, can be quite valuable to collectors, typically ranging from $50 to several hundred dollars, depending on its condition and the specifics of the error. The rarity and appeal of such a minting mistake can significantly influence its market price. If you believe you have one, it's advisable to have it appraised by a professional numismatist for an accurate valuation.
U.K. coins with the denomination "new penny" were only issued from 1971 to 1981. Please check again and post a new question.