<P> A well - known variety in the series is the 1937--D "three - legged" nickel, on which one of the buffalo's legs is missing . Breen relates that this variety was caused by a pressman, Mr. Young, at the Denver Mint, who in seeking to remove marks from a reverse die (caused by the dies making contact with each other), accidentally removed or greatly weakened one of the animal's legs . By the time Mint inspectors discovered and condemned the die, thousands of pieces had been struck and mixed with other coins . </P> <P> Another variety is the 1938 - D / S, caused by dies bearing an "S" mintmark being repunched with a "D" and used to strike coins at Denver . While the actual course of events is uncertain, Bowers is convinced that the variety was created because Buffalo nickel dies intended for the San Francisco mint were repunched with the "D" and sent to Denver so they would not be wasted--no San Francisco Buffalo nickels were struck in 1938, but they were produced at Denver, and it was already known that a new design would be introduced . The 1938 - D / S was the first repunched mintmark of any US coin to be discovered, causing great excitement among numismatists when the variety came to light in 1962 . </P> <P> When the Buffalo nickel had been in circulation for the minimum 25 years, it was replaced with little discussion or protest . The problems of die life and weak striking had never been solved, and Mint officials advocated its replacement . In January 1938, the Mint announced an open competition for a new nickel design, to feature early President Thomas Jefferson on the obverse, and Jefferson's home, Monticello on the reverse . In April, Felix Schlag was announced as the winner . The last Buffalo nickels were struck in April 1938, at the Denver Mint, the only mint to strike them that year . On October 3, 1938, production of the Jefferson nickel began, and they were released into circulation on November 15 . </P> <P> In a 1947 radio interview, Fraser discussed his design: </P>

When did the buffalo nickel stop being made