Ron Guth:
The 1855-O Half Dime is easily the rarest date and mintmark combination of the With Arrows type. It is the only date with a mintage below one million coins. In Mint State, this date is quite scarce and commands a strong premium in grades above MS63. 1855-O Half Dimes in MS66 and better are extremely rare.
This date comes surprisingly well struck, though it is often weak in the denticles. Nonetheless, the strike quality of this date is much better than the other With Arrows Half Dimes from New Orleans and is almost on par with those from the Philadelphia mint.