The 1864-S Half Dollar is scarce in most grades and, like other San Francisco coinage of this period, it is a condition-rarity due to the fact that most of the mintage went directly into commerce and few pieces were saved by collectors. The few Mint State pieces that appear on the market are usually in MS63. Anything better is extremely rare. The best is a single NGC MS67 -- a coin that jumped from $19,550 in 2002 to $74,750 five years later, reflecting its extreme rarity -- it has not reappeared at auction since.
Most examples we've seen are well-struck in the centers with perhaps some weakness on portions of the denticles. The luster is generally soft and satiny.