What is the value of a 1977 D copper dime?

It's difficult to estimate the value of an error coin without an in-person examination. A dime that appears to be fully copper could have multiple causes:

• It could be a so-called lamination error. In the case of a clad coin, a lamination error most often happens when part of the cupronickel cladding fails to bond to the pure copper core either before or after striking. Roosevelt dime lamination errors generally sell for about $6 to $8.
• The coin could be oxidized or otherwise discolored due to exposure to chemicals, heat, etc. In this case it's simply a damaged dime worth face value.
• It could have been plated as part of a school chemistry experiment. Again, it would be simply a damaged coin.