Double Dated Coin Set

When the U.S. Mint changes coin designs, the change usually occurs when production of the old design has ended at the end of a year. On rare occasions, however, the change takes place during the year- resulting in two different coins of the same denomination that bear the same date. Famous examples of this phenomenon are the last Barber Silver Dimes and the first Mercury Silver Dime which were both struck in 1916, and the last Buffalo Nickel and the first Jefferson Nickel which were both struck in 1938.