not worth a plug nickel

obsolete Completely worthless or useless; having little or no value. (A variant of "not worth a plugged nickel.") Refers to coins (not only nickels) that were "plugged"—that is, those that had a hole drilled in their center and were filled with cheaper metals—which made the coins illegitimate and worthless if spotted. Primarily heard in US. I was so excited when my grandpa said he'd give me his car, but this old clunker isn't worth a plug nickel. Over the years working here I've come to realize that the boss's promises aren't worth a plug nickel.