Ron Guth:
The 1840-O No Drapery Half Dime is considerably more rare than the mintage indicates. No other date in the No Drapery Half Dime series is harder to find in Mint State (the closest competitor for that distinction is a fellow O-Mint half dime, the 1839-O). Perhaps the cause of this can be laid at the feet of the New Orleans Mint. What few collectors existed in America in 1840 cared little for mintmarks, so the vast majority of the coins went into (and stayed in) circulation. Fortunately, a few Mint State examples were saved, but their number is tiny, probably on the order of less than two dozen total, and the finest of those is no better than MS64.