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.