what is shield nickel?
It was the first United States five-cent piece to be made out of copper-nickel, the same alloy of which American nickels are struck today.
Shield nickel
The Shield nickel was the first United States five-cent piece to be made out of copper-nickel, the same alloy of which American nickels are struck today. 
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Shield nickel [SEP] Introduction
The Shield nickel was the first United States five-cent piece to be made out of copper-nickel, the same alloy of which American nickels are struck today. Designed by James B. Longacre, the coin was issued from 1866 until 1883, when it was replaced by the Liberty Head nickel. The coin takes its name from the motif on its obverse, and was the first five-cent coin referred to as a "nickel"—silver pieces of that denomination had been known as half dimes. Silver half dimes had been struck from the early days of the United States Mint in the late 18th century.