In 1830, an engraver at the Philadelphia Mint saved the country some money by taking a leftover 1829 die and punching a 3 and a 0 over the 2 and the 9, respectively, then turning the die over to the coiners for production of coins. The result is the only overdate among the Small Diameter Dimes (1828-1837) and one of only four overdate in the entire Capped Bust Dime series. The overdated obverse was used with two different reverses to create the JR-4 and JR-5 die varieties. JR-4 is a common variety, but the JR-5 variety is quite rare (Rarity 5, only 31-75 known). As such, the 1830/29 Dime commands strong premiums in most grades, especially at the higher end.
The 1830/29 Dimes represent approximately one-sixth of the total population of 1830 Dimes. Only a handful of Mint State examples survive. We know of fewer than a dozen different Mint State examples, including the incredible PCGS MS67 JR-5 sold as part of the Pogue Family collection in 2016.