The following information is from my eBook on Type One Liberty Head Double Eagles at http://doubleeaglebook.com/
The rarity profile of this date has been changed more than any San Francisco Type One double eagle struck after 1857. The 1864-S was formerly a rare coin in higher grades, but today it is far more available on account of hoards and shipwrecks.
STRIKE: The 1864-S is, along with the 1862-S, the most poorly defined San Francisco double eagle of this type. Liberty’s hair is typically very weak with little detail seen on the curls and at the top of the head. A few of the higher grade pieces from the S.S. Brother Jonathan show better detail than what is seen on non-shipwrecks pieces. These may show sharper hair and have nearly full radial lines on the obverse stars. With the exception of a few dozen of these coins, the typical 1864-S has a “pancake” obverse with considerable overall flatness. The reverse on all examples tends to be better struck. The usual weakness on the wing tips and tail feathers is seen, but the rest of the detail is reasonably sharp. Some coins have a network of fine die cracks through the reverse lettering.
SURFACES: The pieces found on the S.S. Brother Jonathan tend to show fewer abrasions than the S.S. Republic coins or pieces not from shipwrecks. The typical non-shipwreck 1864-S is extensively abraded, to the point that these marks are clearly detracting. Locating a non-shipwreck coin with choice surfaces is possible but it is difficult.
LUSTER: The luster is similar in quality and texture to that seen on other San Francisco double eagles from this era. Higher grade pieces are frosty with a slightly grainy texture. Certain shipwreck coins have better than average luster for the issue and these represent most of the high end, cosmetically appealing 1864-S double eagles currently available to collectors of Type One double eagles.
COLORATION: The natural coloration is most often a medium rose-gold or orange-gold shade. There were some coins from the shipwrecks which had nice color, especially from the S.S. Brother Jonathan. On coins not from the shipwrecks, the color tends to be less intense in hue as many have been cleaned or dipped.
EYE APPEAL: Non-shipwreck 1864-S double eagles have well below average eye appeal. The typical piece is not well struck, has inferior luster and shows numerous abrasions. There are shipwreck coins with comparatively good eye appeal and these clearly have better luster and detail than their counterparts.
INTERESTING VARIETIES: All 1864-S double eagles have a very large date and a very small mintmark. There are no significant die varieties known.
HOARDS: There were 108 in the S.S. Brother Jonathan hoard including around three dozen graded between Mint State-60 and Mint State-63 by PCGS. Another six dozen or so were graded in About Uncirculated. A total of 153 were found in the S.S. republic including 60 in Uncirculated.
BUYING TIPS: Most of the high-grade 1864-S double eagles are from a shipwreck. In my opinion, it is worth paying a premium to purchase an example from one of the two major hoards in its original holder. Some Uncirculated 1864-S double eagles have been upgraded and are now in secondary NGC or PCGS holders.
AUCTION RECORD: The auction record for this date is $115,000 which was set by Heritage 1/12:5042.
FINEST KNOWN: The single finest known 1864-S double eagle is an NGC MS65 which was last sold as Lot 5042 in Heritage’s January 2012 FUN auction.
TOTAL KNOWN: 2000-2500+
Very Fine: 800-900
Extremely Fine: 700-900
About Uncirculated: 375-450
POPULATION FIGURES: As of the beginning of 2015, PCGS had graded nine in MS60, 21 in MS61, 13 in MS62 and three in MS63 for a total of 46 in Uncirculated. NGC had graded 21 in MS60, 65 in MS61, 27 in MS62, seven in MS63 and one each in MS64 and MS65. This includes 63 from the S.S. Republic and 23 from the S.S. Brother Jonathan. NGC has graded 122 in Uncirculated in total. These figures are extremely inflated by resubmissions, especially in MS61 and MS62.
PERFORMANCE SINCE 2002: Due to the sale of the Bro Jo coins in 1999, we are going to use this as our comparative date, not 2002 when these coins were selling at a discount. In the current market, a choice About Uncirculated 1864-S double eagles (equivalent to AU55) is worth in the area of $3,500-4,000; more if the coin is in its original Brother Jonathan holder. In 1999, dozens of AU55 examples were auctioned in the $3,500-4,500 range. In the current market, an average quality Uncirculated example (equivalent to MS61) is worth $13,000-16,000. In 1999, a number of MS61’s sold at auction for $7,000-8,000. This date has not shown strong performance. However, many of the coins in the original Bro Jo holders have been broken out and upgraded so these have, in theory, shown better than average performance.
COMMENTS: The S.S. Republic examples of this date tend to have a much different appearance than the coins from the S.S. Brother Jonathan. The former tend to have more vivid luster while the latter are more subdued and a bit more matte-like. Many collectors add an example from both wrecks for their set and the 1864-S is a good issue to do this for, given the different appearance of the two shipwrecks.
David Akers (1975/88):
The 1864-S is quite rare by S-Mint standards and is on the second level of rarity along with such other dates as the 1854-S, 1860-S, 1861-S, 1862-S, 1866-S Motto, 1867-S and 1868-S. Strictly graded AU specimens are decidedly rare and true mint state pieces are very rare. If a choice or gem uncirculated 1864-S exists, I have not seen it.