Ron Guth: 1840 was a transitional year for half dimes. The earliest versions were of the No Drapery type, which lacked the fold of drapery under Liberty's left arm (viewer's right). Later versions showed a modified design, now with drapery, a redesigned rock, and an upright shield. Of the two versions, the No Drapery is easily the most common.
Close examination of the image shown above of the PCGS MS68 reveals a heavily cracked die which was about to break up into three larege chunks. These breaks are not universal to 1840 No Drapery Half Dimes, but they add interest to this date. Collectors will have little to no difficulty finding Mint State versions of this variety, as dozens have been certified in each of the MS62, MS63, and MS64 grades.