Ron Guth:
Though other dates in the 1840's have lower mintages than the 1847-O, few of these seem to have made it into collectors' hands. As a result, in top grades, this date is the third most valuable of the decade (after the 1849-O and the 1842-O Small Date). This fact is reflected not only in the price guides, but also in the PCGS Population Report, where, conicidentally, only the 1849-O and 1842-O Small Date have lower Mint State populations. For the 1847-O Quarter Dollar, PCGS shows only 1 MS62, 2 MS63s, 1 MS64, and none finer.
The PCGS MS62 illustrated above shows a good strike and strong details, which is a bonus coming from a Mint that is often associated with soft strikes.