Complex sentence: A similar case occurred in 1938, when a reverse die for the buffalo nickel was made for the San Francisco Mint, because that year only, the Denver Mint made these coins with a "D" punched over the "S".
Split into simpler sentences: A similar case occurred in 1938 when a reverse die for the Buffalo nickel was made for the San Francisco Mint. Because that year only the Denver Mint made these coins a "D" was punched over the "S".