The following information is from my eBook on Type One Liberty Head Double Eagles at http://doubleeaglebook.com/
The 1864 is not as scarce as the 1862 or 1863, but it is a tough and popular Civil War date. Until the discovery of 17 Uncirculated examples in the S.S. Republic (see below), this date was almost impossible to find in higher grades.
STRIKE: The quality of strike seen on this issue varies. There are some coins which are very well struck, even at the center of the obverse and on the hair. Others show visible weakness at the curls around the face but are stronger on the reverse. In fact, the reverse is nearly always better struck than the obverse, with sharper wing tips and tail feathers than one might expect. Weakness is sometimes seen on the top of the letters in the value. Light die cracks are seen through the obverse stars on the left and at the top of the lettering on the reverse.
The S.S. Republic coins tend to show sharp strikes for the date although some can show weakness on the curls around the face.
SURFACES: Most 1864 double eagles are extensively abraded with numerous detracting marks in the fields. They do not tend to be as deep as those seen on 1862 and 1863 Philadelphia double eagles, but they do tend to be noticeable. Many have been cleaned or dipped and show hairlines as a result. It is possible to locate a piece with acceptable surfaces but these are not easy to find.
The S.S. Republic coins may show small clusters of marks in the field (especially the left obverse) but they are still far cleaner than the other known 1864 double eagles. These coins do not have a typical “sea water” look and the appearance is extremely pleasing.
LUSTER: This date has better luster than the 1862, 1863, and 1865 Philadelphia double eagles. High-grade pieces show rich frost which is different in texture than on the other Philadelphia issues from this era.
The S.S. Republic coins have excellent luster which shows a different texture. It is more satiny and it is easy to differentiate between these coins and examples which were not from this shipwreck.
COLORATION: The natural coloration is very attractive with medium to deep green-gold or medium yellow-gold and rose hues. It has become hard to find an 1864 double eagle with good color as many have been dipped or processed. Choice, original examples with good color are worth significant premiums over typical coins.
The S.S. Republic coins have distinctive light green-gold and yellowish hues which I find to be extremely attractive
EYE APPEAL: The 1864 double eagle has average eye appeal. The typical coin has good detail but shows many marks in the fields from extensive use in circulation or from bag wear. The luster and natural color may be good, but CAC-quality coins are very scarce and command a 25+% premium in the current market.
The S.S. Republic coins tend to have superior eye appeal and many of the best looking 1864 double eagles are from this source.
INTERESTING VARIETIES: All 1864 double eagles have a large date that is placed far to the right. No significant varieties are known.
PROOFS: A total of 50 Proofs were struck. This is the most available Type One issue in Proof with as many as 13 to 15 known. The finest known is a superb Proof-67 Ultra Cameo graded by NGC which is one of the two finest known Type One double eagles of any date in Proof.
As of the end of 2014, PCGS had graded two in PR64, four in PR64CAM, one in PR64+CAM and one in PR65 Ultra Cameo for a total of eight. NGC had graded one in PR63CAM, four in PR64CAM, two in PR64 Ultra Cameo, two in PR65 Ultra Cameo and one in PR67 Ultra Cameo for a total of ten. These figures are inflated by resubmissions. CAC has approved a single PR64.
The current auction records for a Proof 1864 double eagle are $359,375 for an NGC PR65 Ultra Cameo offered as Heritage 1/11: 5278 and $352,500 for an NGC PR65 Ultra Cameo, sold as Heritage 8/12: 5423.
HOARDS: A total of 25 were found on the S.S. Republic including 17 in Uncirculated. Prior to this, no hoards containing 1864 double eagles had ever entered the market.
BUYING TIPS: Thanks to the discovery of some exceptional examples on the S.S. Republic, this date is now available in Uncirculated. When these coins were announced, I felt that the market for higher grade 1864 double eagles would crash but the exact opposite has happened. Today, the level of demand far exceeds the relatively low supply.
AUCTION RECORD: The auction record for a business strike 1864 double eagle is $282,000, set by Heritage 4/14: 5812. This same coin, in an NGC MS64+ holder, had sold for $207,000 as Heritage 8/11: 7651.
FINEST KNOWN: The finest known is a PCGS MS65 which is owned by a New England collector. I purchased it for him out of the Heritage 2014 Central States sale for $282,000.
TOTAL KNOWN: 600-700
Very Fine: 100-150
Extremely Fine: 200-235
About Uncirculated: 275-280
POPULATION FIGURES: As of the beginning of 2015, PCGS had graded 15 in MS61, 10 in MS62, three in MS63, and one in MS65 for a total of 29 in Uncirculated. NGC had graded three in MS60, 13 in MS61, seven in MS62, two in MS63, and one in MS64 for a total of 26 in Uncirculated. This includes 18 Uncirculated coins from the S.S. Republic. These figures are significantly inflated by resubmissions, especially in MS61. CAC has approved seven Uncirculated examples, one in MS60, two in MS61, and four in MS62.
PERFORMANCE SINCE 2002: In the current market, a choice About Uncirculated example of this date (equivalent to AU55) is worth in the $9,000-11,000 range. In 2002, when the first edition of this book was published, a similar coin was worth in the area of $2,500 to $3,500. In the current market, a choice Extremely Fine example of this date (equivalent to EF45) is worth $5,000-6,000. In 2002, a similar coin would have sold for $1,000-1,500. The price performance of the 1864 double eagle rivals that of any date in the Type One series in the last decade. Clearly, it was very undervalued in 2002. Today, it has multiple levels of demand as it is sought by Civil War collectors and Type One specialists alike.
COMMENTS: The finest known 1864 double eagle is a recent discovery which wasn’t known when the first edition of my book was published. It walked into Heritage’s New York offices and was sent to NGC where it graded MS64+. It was soon auctioned where it brought $207,000. After this it was upgraded to MS65 by PCGS (the grade I thought it always should have received) and purchased by a client of Monaco Rare Coins. A few years later, I bought it at auction for $282,000 and placed it in a New England collection. This remarkable coin was clearly not a shipwreck piece from the S.S. Republic.
David Akers (1975/88)
This is another of my favorite dates of this type. It is very scarce in all grades, comparable overall to the 1855, 1856, 1857, 1858 and 1863, and just a little less rare than the 1862.