Ron Guth:
All 1823 Dimes are overdates that show a clear 3 over an underlying 2. On the reverses of 1823/2 Dimes, the E's in the legends will be either larger or smaller than the adjacent lettering. Two distinct die varieties make up the entire Large E's population.
In 1984, Davis et al claimed to know of at least six specimens in MS60 or better. PCGS has certified several examples in MS63 to MS66. The finest example is the PCGS MS66 in the High Desert Collection. D. Brent Pogue's example was certified as a PCGS MS65.