The 1811/9 Dime is the only variety known for this year, thus all 1811 Dimes are overdates.
The mintage for this date is very low in comparison to other dates in this series. At 65,180 coins, this date has the second lowest mintage, and even that is not much more than the mintage of the scarce 1809. Compare those mintages with dates such as the 1821 (mintage of 1,186,512) or 1827 (1,215,000 coined).
As might be expected, finding an 1811 Dime is not such an easy task. PCGS (as of September 2011) reports only 70 examples, in all grades, on their Pop Report. Of those, only 16 examples are Mint State. Among the Mint State examples, MS-63 is the most common grade. The finest examples certified by PCGS are two MS-66s.