Prior to casting the 2000 Sacagawea dollar in limited amounts around the turn of the century, the U.S. Mint experimented
1999-P Experimental Delaware State Quarter
with several alloys, which is why they are exceptionally uncommon (a high-graded specimen went for $4,888 at auction).
1999-P Experimental Delaware State Quarter
Although it's not very hard to locate this coin, its worth comes from how hard it is to find one in pristine condition.
2003-D Maine State Quarter
This coin is unique since it is seldom seen in almost flawless condition.
2000-P South Carolina State Quarter
The "extra low leaf" variety is valued at almost $1,500 because an additional leaf was purposefully placed to the corn ear on the left, according to some.
2004-D Wisconsin State Quarter (Extra Leaf Low)
A "broadstruck" manufacturing mistake raises the value of this state quarter to $25, over a hundred times its face value.