The following information is from my eBook on Type One Liberty Head Double Eagles at http://doubleeaglebook.com/
When analyzing the rarity of New Orleans double eagles, the 1854-O and the 1856-O are obviously in a class of their own. In the next tier are issues such as the 1855-O, 1859-O, and 1860-O. I regard the 1855-O as the rarest of these three, especially in About Uncirculated and higher.
STRIKE: The 1855-O is not as well-struck as some of the earlier double eagles from this mint, but it is sharper than such issues as the 1859-O and the 1860-O. The hair is usually relatively well detailed although the curls below Liberty’s ear and the top of the head may show some weakness. The stars are sharp with the exception of the first and the sixth through the ninth which are typically weaker. The reverse is a bit better struck with above average detail seen on the feathers and the wingtips. The mintmark is usually weakly impressed, especially on the left side.
SURFACES: As with all of the second-tier rarity issues from this mint, it is hard to locate an 1855-O with choice surfaces. I have seen a few more reasonably mark-free pieces, though, than I have for the 1859-O and the 1860-O. Many examples show detracting bagmarks and there are more than a few with mint-made chips or defects in the planchet. An 1855-O double eagle with above average surfaces is very rare and desirable.
LUSTER: This is an issue with good quality luster. Higher grade pieces have either semi-prooflike or frosty fields. It is very difficult to locate an 1855-O which has not been cleaned or dipped and which has had its mint luster stripped as a result.
COLORATION: The color seen on original undipped 1855-O double eagles is an attractive deep greenish-gold. I have seen a few others with medium to deep green-gold hues. Most examples have been cleaned or dipped to the point that they no longer display their natural color.
EYE APPEAL: This issue generally is found with below average eye appeal. This is due to the fact that many have been cleaned or dipped. There are a small number of attractive, original pieces which grade in the Extremely Fine-45 to About Uncirculated-55 range and these command substantial premiums over typical washed-out examples.
INTERESTING VARIETIES: All 1855-O double eagles have Slanting (or Italic) 5’s in the date. There are no significant varieties known.
PROOFS: No Proofs of this date were struck.
HOARDS: There were three AU58 examples in the S.S. Republic treasure. All were sold to collectors via private treaty sales, and none have appeared at auction or on the open market.
BUYING TIPS: For many collectors, the 1855-O will represent the most significant O mint double eagle in the Type One set. Therefore, this is a purchase which should be taken seriously. Be patient and wait for the right coin and don’t be afraid to stretch for a choice, original coin as these truly deserve a premium.
AUCTION RECORD: The current record price for this date is $141,000 set by an NGC MS61 sold as Heritage 1/14: 5517.
FINEST KNOWN: The highest-graded 1855-O is an NGC MS61 which recently sold for $141,000 as Heritage 2014 FUN: 5517. However, I think that the PCGS AU58 coin in the Crawford collection is a nicer coin and I would rank it as the finest known without much hesitation.
TOTAL KNOWN: 80-90
Very Fine: 43-45
Extremely Fine: 21-27
About Uncirculated: 12-16
POPULATION FIGURES: As of the beginning of 2015, PCGS has yet to grade a single 1855-O in any Uncirculated grade. The best they have graded are four in AU55 and two in AU58. PCGS has recorded a total of 19 in the various AU grades. NGC has graded two in MS60 and one in MS61 for a total of three coins in Uncirculated. They have recorded a total of 23 in the various AU grades. The population figures for this date in all AU grades are inflated by resubmissions. CAC has not approved any Uncirculated examples, and only one AU, an AU55.
PERFORMANCE SINCE 2002: In the current market a Choice Extremely Fine example of this date (equivalent to an EF45) would sell in the $30,000-35,000 range. The same coin would have sold for $15,000-20,000 in 2002. In the current market, a Choice About Uncirculated example (equivalent to an AU55) would sell in the $55,000-65,000 range. The same coin would have sold for $25,000-35,000 in 2002. This date has not had the same robust price appreciation as many other rarer New Orleans double eagles have had in the past decade. It is hard to call such an expensive coin “undervalued” but it seems to me that in EF45 and AU55 grades, the 1855-O could easily rise significantly in price and still not seem “overvalued.”
COMMENTS: The pattern of availability for higher grade 1855-O double eagles is odd. A whopping eight examples in higher grades (AU50 and above) have sold at auction since the middle of 2011. In the five years prior to this (2005 to 2010) only five higher grade AU’s had sold at auction. Part of this was due to one or two collectors accumulating a few examples of this date and then selling them.
David Akers (1975/88):
This one of my favorite Double Eagles. I think that it is one of the most unappreciated coins in the series and it is undeniably one of the rarest, especially in high grade. It is not quite as rare overall as the 1854-O and 1856-O but the difference in rarity is not as great as the price differential would imply. Furthermore, I feel the 1855-O is actually rarer than either the 1854-O or 1856-O in high grade and is one of the two or three rarest Double Eagles with respect to condition rarity. Although there are several auction records for AU's, I have never seen one at that level. The two finest specimens I know of are the choice EF-45's in a prominent Dallas bank collection and the Eliasberg Collection and I have seen a few other solid EF-40's. Most of those I've encountered were only VF and, in truth, this date is not often seen in any grade. Not included in the 443 sales used in this analysis were two sales (Deetz, Stack's 1946 and C. W. Green, Mehl 1949) that contained specimens graded "uncirculated." I have not personally examined either of those coins and therefore cannot vouch for their condition. However, based on what I have seen and heard of, I am skeptical that they would grade uncirculated by today's standards. The 1855-O is always semi-prooflike or prooflike.