There are many reasons for the 1974 quarter error, but the most striking one has to do with the design of the coin. The New Hampshire quarter design features the Old Man of the Mountains, a natural wonder that collapsed two years after it was released. Apparently, the designers did not know about the error until after the coins were released. So, how did they fix the mistake? There are several reasons, and you can read about them below.
Since their introduction in 1932, the Washington Quarters have undergone several changes, most notably the reverse design, which is now a design commemorating the nation’s national parks. The Philadelphia mint minted three million of the 1974 quarters, while the Denver mint minted 353,160,000 of the same coin type. While the Philadelphia mint produced the majority of the 1974 Washington quarters, the Denver mint minted the remaining 353,160,000 coins.