Limited Edition Proofs: Special proof versions of coins that were minted in extremely limited quantities.
Notable Mint Errors: Coins with significant minting errors, such as double denominations or misstrikes.
Historical Context: Coins tied to pivotal moments in history or with connections to prominent historical figures.
Exceptional Grade: Coins that are among the highest graded examples known to exist.
Special Releases: Coins released as part of a special commemorative set with a limited number of pieces.
Though a Bicentennial quarter valued at nearly $850 million is improbable, it underscores the fascinating and sometimes surprising potential worth of collectible coins.