The U.S. Mint issued quarters sporting designs to commemorate each of the 50 states over a 10-year period beginning in 1998. The rarest of these quarters are those with low production orders and ones with striking and printing errors, such as some Wisconsin quarters.
Among the 450 million Wisconsin quarters created in 2004, only a few thousand sport an extra leaf on the ear of corn in the design. These coins have a slightly higher value due to their rarity. Coins featuring the "S" mint mark are also rare, as these were struck in San Francisco as proof sets and were not intended for circulation.