In 1840, the design on the Half Dime underwent some major reworking to balance out the elements and give the "Liberty sitting on a rock" motif a more triangular appearance. The bulge in the rock on the left side of the coin was lessened, the shield was moved into an upright position, and drapery was added underneath Liberty's arm on the right side of the coin. Once these changes were made, the Mint struck additional half dimes in 1840, about a third less than the mintage of the 1840 No Drapery Half Dimes (the number of survivors certified by PCGS is approximately four times less, so the relative mintage figures appear accurate).
In Mint State, the 1840 With Drapery Half Dime is tough, but not overly so. Mid-grade examples, such as MS64 are available...for a price. Above MS64, this date becomes very rare. The finest example is a single PCGS MS67.