The 1842-O Dime is a surprising coin simply because it has a relatively large mintage for the early 1840s, yet it is a very rare and desirable coin in high grade. For instance, in MS63, the PCGS Price Guide shows the 1842-O valued at nearly ten times that of the 1842 (which has a lower mintage). This is because very few nice examples of the 1842-O Dime were saved by collectors, few of whom lived in or around New Orleans. Thus, finding a Mint State example of this date is quite a challenge. Then, trying to find a Gem example is like searching for a hen's tooth. Not undexpectedly, the price record for this date was set by one of the extremely rare PCGS MS65's sold by Heritage in 2010.
The strike quality for this date is inconsistent, though most examples show some weakness on the bow and ribbon on the reverse.
Gerry Fortin identified seven different die varieties for this date, including some with Small or Medium-sized mintamrks.