Eight varieties comprise the entire mintage of 1830 Dimes. Seven of the varieties have what is known as a "Medium 10C"; the eighth variety has what is known as the "Small 10C." The authors of the standard reference book assigned the number JR-2 to the Small 10C variety and assigned it Rarity 1 (common). Their Condition Census includes "at least ten mint state pieces...", the finest of which is an "MS-67" in a 1982 ANA sale.
The PCGS CoinFacts Condition Census includes seven Mint State pieces, the finest of which is a single MS-64. For a coin that is supposedly so common, it is quite difficult to locate a Mint State example.
Sources and/or recommended reading:
Davis, David J. et. al. Early United States Dimes 1796-1837: A Reference Book of Their Types, Varieties and Rarity. Ypsilanti, MI: John Reich Collectors Society, 1984.