Mint records indicate a total mintage of 17,996 pieces of the 1822 Half Eagle. Within the series this is not an extraordinary number by any means. Both 1823 and 1824 had lower mintages, while other years did not see a much larger quantity produced. Yet, while those dates are rare, they are represented by a far greater number of survivors compared to the 1822 half eagle. There are several explanations which have been offered for this unusual situation.
First of all, these early United States gold coins were heavily exported to overseas countries, in particular Europe and China. Once overseas in most cases the coins were melted and never returned, although occasionally a bank vault is opened which contains some rare United States gold coins. No 1822 half eagles, however, have ever been found in overseas countries. While this scenario is very well possible and might have played a part in the creation of this ultra-rarity, the next two possibilities are more likely.
Despite the lack of any supporting Mint documentation, it is very well possible that the majority of 1822 half eagles were retained at the Mint for a number of years and were subsequently melted. This would be a situation that is very similar to that of some of the double eagles of the 1920s and early 1930s. Despite being produced in reasonable quantities, some of these dates are extreme rarities represented by only a few dozen examples. We know that melting played an important role in the case of these double eagles, as confirmed by Mint documentation and supporting stories from people present at the Mint at this time. For the 1822 half eagle, however, these stories are not present, although this possibility is still very plausible.
The last possibility is that the mintage of 17,996 is incorrect. We know that, for cost-saving reasons, dies of other years were often used to produce coins in years other than listed on the coins. Many series have had extensive research done to determine how many coins were truly minted for any particular issue. This can be done because certain dies were used throughout various years and die states can provide valuable information. Combined with delivery records, researchers have been able to determine full emission sequences of many early American coins. In case of the 1822 half eagle, however, this is more difficult, as both obverse and reverse dies were only used in this year. Yet, this appears to be the most plausible theory to explain the extreme rarity of this issue.