I have a Jefferson 5 cent coin that appears to be solidly copper. Is it an error and have any additional worth?
Can't be sure without seeing good clear photos of both sides of the coin. In all probability, (without seeing photos) it's been copper-plated as a novelty item, or has environmental surface issues. Photos, please - we'll be glad to tell you exactly what it is.
Most likely Environmental Damage. Nickels do not have a clad layer so it can't be missing the clad layer. Here are some of my metal detected examples Bottom row are normal nickels.. Worth? 5 cents
You could have a copper nickel if it is the size of a cent and accidentally was minted on a copper cent planchet. But it's almost 100% what Paddy has said/ described. The nickel on penny stock is an interesting idea. What year is this nickel? If it is 1983-present, no copper pennies then.
you can do it the fun way. Mason jar, water some salt a pre 1982 penny and a nickel...oh, and a 9v or better battery and some copper wire. Do like the Egyptians!!!
Last time I went hunting I found 2 cigarette box top papers, a bottle cap from an RC cola bottle and 2 pull tabs....and dirt under my nails for 3 days. I have no luck.