1998 P Nickel on front, partial penny on back

It is immediately obvious to anyone who’s seen any kind of misstruck coins.
Plus, glue or adhesive buildup on coins is not metal, and with any kind of examination, it is obviously foreign material on the coin rather than part of the coin itself.

Inexperienced folks are sometimes tricked by it because the glue can have a clear color, and it can retain imprints of the design details of other coins that got stuck to the original coin due to the glue, making it look like some kind of weird “error”.

But it is not difficult at all to distinguish.