What this coin looks like (obverse, reverse, mint mark location, special features, etc.): There were a few major varieties of the 1827 Capped Bust Half Dollar. Two of them deal with the styling of the number "2" in the 1827 date. One variety had a curved and curled base on the "2" while the other variety had a perfectly flat and square base on the number "2". The difference between the 1827 Curl Base 2 vs Square Base 2 is depicted above in the example comparison image.
The other major variety is an 1827/6 overdate error in which the 1827 date was struck over an 1826 date which resulted in a 7 over 6. A large portion of the underlying 6 can be seen to the right of the 7 and also a small portion under the top crossbar of the 7. The bottom of the "7" is also larger and thicker - and also droops down a bit towards the rim of the coin. An example of the 1827/6 half dollar overdate and its features are depicted below in the example image: