You can buy a novelty set of miniature coins at some stores. They are of course reproductions and not actual shrunken coins.
Somebody was very, very bored. Looks like they plated a genuine nickel in gold, measured the mini nickel, drilled a hole of corresponding size into the plated nickel, and smashed the mini nickel into said hole. Looks like they have also attempted to melt them together.
No extra value, but that is the coolest post-mint damage I think I have ever seen.