Ron Guth: The 1838 Half Dime is found in two major varieties: Large Stars and Small Stars. Actually, the Small Stars variety started out as a Large Stars die that was subsequently ground down to remove clashmarks, thus reducing the apparent size of the stars.
Based on the PCGS Population Report, the Small Stars variety appears to be ten times as rare as the Large Stars. Most of the Mint State examples certified by PCGS appear in the MS-63 and MS-64 grades. The finest examnples certified by PCGS (as of April 2011) are two MS-65s.