What is the value of a 1971 silver penny?

I am a 25 year coin collector and to my knowledge, there is no such coin produced by the us mint. It may be a silver plated coin done by a collector or enthusiast. In this case it would only be worth face value. ALL 1971 U.S. cents were minted in bronze. Any "silver" penny is most likely plated, although it's possible that your coin could be what's called an off-metal strike. At that time the Mint contracted production of foreign coins and sometimes a blank for one of them would get mixed in with normal U.S. blanks. The best way to make an initial determination would be to weigh the coin; a genuine U.S. bronze cent would weigh 3.11 gm and a plated one would be a tiny bit more.