Initially, there were only 14,485 of these coins when they were originally minted. However, there are approximately only 100 or so survivors left in all grades combined. Despite the rarity of this date, it is relatively common when compared to other half eagles from the 1820s. In fact, it is the most available date between 1821 and 1829.
This variety is known as the Large 8, 13 stars reverse. As you can see, the 8 appears larger than the rest of the numbers. If one looks at the reverse, they will find 13 stars, which is expected on these coins. However, there is also a 14-star variation. These stars were not meant to represent the states, as there were already 15 states at this time. Simply, the engraver added an additional star by accident when creating the die. So, with a mintage of 24,867, the Large 8, 13-star reverse is the more common variety. Typically, one sees this coin available in VF grades with uncirculated examples only being occasionally available.
There are two varieties for this example, Large D and Medium D. The best way to differentiate is to see if the mint mark is wider or taller. If it is wider, than it is most likely a medium example. If it is the latter, then it is most likely a large example.