Coins in exceptionally high grades, such as MS-70 or Proof-70, can be worth more than their circulated counterparts.
The U.S. Mint produced a limited number of 40% silver-clad Bicentennial Quarters. These are worth more than the regular clad versions.
Any Bicentennial Quarter with a mint error, such as a double strike or off-center error, could be more valuable.
Quarters that were part of special mint sets or first strikes might carry a premium.
Coins that have been professionally graded and certified may fetch higher prices.