There is a special gem among the quarters struck in Denver. Due to a minting error, a small quantity of 1976-D quarters have a unique mark next to the eagle's breast that is referred to as the "D Mintmark Variety."
The 1976-S proof coin is San Francisco's contribution to the tale of the Bicentennial quarter. This coin, struck using specially prepared dies and planchets, has finer details and sharper images.
Two distinct varieties, Type I and Type II, emerged as a result of a subtle design alteration that happened during the production of the Bicentennial quarters. With its sharper lettering and torch flame details,
Occasionally, minting errors give rise to exceptional rarities, as demonstrated by the Bicentennial quarters struck on silver planchets.
Bicentennial quarters with the 1976-D double die obverse varieties are highly valued. Coins with strong doubling on the obverse features, especially the date and lettering, have commanded prices exceeding $40 million in the numismatic market.