plugged/plugged nickel

Before I Say Good-Byeを読んでいます。BrennanとSclafaniは刑事です。
“Mr. Lang, we appreciate how busy you are,” George Brennan said soothingly.
“But I’m sure you can understand our need to ask you a few questions. You went to see Nell MacDermott yesterday, didn’t you?”
Lang raised an eyebrow. “Yes, I did. What of it?”
He didn’t like having that brought up, Sclafani thought. Up till now, he’s been on his own turf and feeling pretty sure of himself. But all his money and looks and background won’t be worth a plugged nickel if we can hang a quadruple murder on him, and he knows it, not worth a plugged nickel.
"plugged nickel" の意味は何でしょう？　"plugged" を辞書で引くと次の意味が出てきました。
・WordNetadjective: (of a coin) altered by the insertion of a plug of base metal
すると、"plugged nickel" は変造された５セントの様ですが、辞書をよく見ると "plugged nickel" で次の意味があることが分かりました。
・The Dictionary of American Slang: Valueless : His word isn't worth a plugged nickel
・McGraw-Hill's Dictionary of American Slang and Colloquial Expressions: worth little or nothing. This new battery is not worth a plugged nickel.