The following information is from my eBook on Type One Liberty Head Double Eagles at http://doubleeaglebook.com/
The 1855 double eagle is generally regarded as a common date in the Type One series. It is actually scarce in the higher About Uncirculated grades and it is very rare in any Uncirculated grade.
STRIKE: This is a well-struck issue. The obverse shows good detail at the center with sharp hair. On some, there is weakness on the top strands of hair. Many show full definition on the stars and the denticles on the obverse. The reverse is also well struck with most of the details clear except for the tips of the wings. On some, there are light clashmarks on the obverse and the reverse. Late die states show fine cracks at the tops of the lettering on the reverse.
SURFACES: The 1855 is very difficult to locate with clean surfaces. Most are heavily abraded with deep, detracting marks in the fields. Sometimes, these marks are clustered on focal points such as the cheek and these can be especially detracting. Some of the diagnostic features that are seen on this date include a small area of die rust below the bottom left of the I in LIBERTY, and a number of die lines which go from the curls to the base of the TY in LIBERTY. These are not always visible on lower grade coins.
LUSTER: The luster is below average. It is satiny in texture and it typically appears subdued or even a bit dull. This is compounded by the fact that many examples have been cleaned or dipped. There are a few choice pieces which show good luster and these are very desirable.
COLORATION: The natural coloration on 1855 double eagles is either a rich medium yellow-gold or a deeper green-gold. Most have been cleaned or dipped at one time and pieces with original color atop choice surfaces are very scarce.
EYE APPEAL: This is a date which tends to be found with below average quality eye appeal. Most have been cleaned or dipped and often are heavily abraded as well. Coins with good color and luster are very scarce and should command a strong premium.
INTERESTING VARIETIES: All are found with Slanting (or Italic) 5’s in the date. Breen states that varieties are known with Normal, Heavy, and Thin dates, but it is probable that these variations are either die states or relate to how well a specific coin is struck.
PROOFS: No Proofs of this date were struck.
HOARDS: 16 examples were found in the S.S. Republic treasure including two in Uncirculated. Seven were found in the S.S. Central America, while six were uncovered in the Baltimore Hoard.
BUYING TIPS: You can still purchase a nice quality 1855 double eagle for less than $5,000, and I think this is one of the better values in a series which doesn’t have many undervalued coins due to its large collector base.
AUCTION RECORD: The auction record for this date is held by ANR 3/06: 1704, graded MS64 by PCGS, which sold for $126,500. This is by far the finest known for the date, and it was earlier sold in Stack’s session of Auction ’84.
FINEST KNOWN: This date has a clear finest known and it is the PCGS MS64 in the William Crawford collection. It is ex ANR 3/06: 1704 and it sold for $126,550. The next best is a PCGS MS63 which sold for $69,000 as ANR 8/06: 1607. It is an interesting coincidence that the two finest known 1855 double eagles appeared for sale within a few months of each other in 2006, and both were sold by the same firm.
TOTAL KNOWN: 900-1100+
Very Fine: 300-400
Extremely Fine: 370-400
About Uncirculated: 215-280
POPULATION FIGURES: As of the beginning of 2015, PCGS had graded two in MS60, seven in MS61, three in MS62, two in MS63, and one in MS64 for a total of 15 in Uncirculated. NGC has graded six in MS60, eight in MS61, two in MS62, and one in MS64 as well as a pair of MS60 coins from the S.S. Republic for a total of 19 in Uncirculated. These figures do not appear to be overly inflated by resubmissions. CAC has approved just one of each in MS60, MS61, and MS62.
PERFORMANCE SINCE 2002: In the current market, a Choice Extremely Fine example (equivalent to an EF45) is worth in the area of $2,250-3,250. In 2002, a similar coin was worth $600-800. In the current market, a Choice About Uncirculated example (equivalent to AU55) is worth in the area of $3,250-4,250. In 2002, a similar coin was worth $1,500-2,000. The price performance of this date is not as impressive as many less scarce dates in the Type One series, leading me to believe that it is still undervalued.
COMMENTS: The 1855 is not often seen above properly graded About Uncirculated-55 to About Uncirculated-58 and I doubt if more than a half dozen exist which grade Mint State-62 or finer. The Philadelphia issues from 1854 through 1858 remain highly undervalued and offer the savvy collector an excellent opportunity to purchase truly scarce coins at prices which are still reasonable.
David Akers (1975/88):
The 1855 is quite scarce in any condition and in mint state it is definitely rare. Overall, it is similar in rarity to the 1856, 1857, 1858, 1863 and 1864 among Type I Double Eagles. I have seen several uncs that I would call choice (MS-63) but I have never seen one that would qualify as a gem by today's standards, nor have I ever heard of one. The typically available specimen is VF or EF and all examples of this date that I have seen were frosty.