Ron Guth: When the new Liberty Head Nickel was introduced in 1883, no one at the Mint noticed (or cared) that the word "CENTS" was missing from the reverse. The omission was noticed by certain enterprising individuals who, quick to seize an opportunity to make a quick buck, gold-plated the coins and passed them off as Five Dollar gold pieces. These became known as "Racketeer" Nickels. True "Racketeer" Nickels should be in very high grade and the edge should be reeded (this was done by hand to mimic the edge reeds on a gold piece). Modern versions are usually low grade and their edges are smooth; they have been produced by the tens of thousands and are, in effect, rip-offs of a rip-off!
Later in 1883, the Mint corrected the reverse by moving "E PLURIBUS UNUM" to top center and replacing it with a bold "CENTS".