The following information is from my eBook on Type One Liberty Head Double Eagles at http://doubleeaglebook.com/
Production of double eagles at the San Francisco mint increased dramatically in 1855. This is the most available of the three double eagles struck during this year.
STRIKE: The 1855-S is one of the better-made Type One double eagles from this mint. The obverse shows good hair detail with clear separation on many of the curls. The stars generally show full radial lines and the denticles are clearly separated. On the reverse, the wingtips are sometimes weak but the rest of the detail is sharp. The edges usually show a distinctly beveled appearance.
SURFACES: The great majority of 1855-S double eagles display detracting marks on the surfaces. Some have noticeable scratches or deep reeding marks in the fields from contact with other coins. But with some patience, the collector should be able to find a reasonably clean example.
LUSTER: The luster is frosty and it appears a bit subdued in comparison to the Philadelphia coins of this era. On the high grade pieces from the S.S. Central America, the luster has more of a satiny appearance.
COLORATION: The natural coloration for the 1855-S double eagle is a medium to deep orange-gold or rose-gold. Well circulated pieces appear to have a deeper green-gold hue. Coins from the S.S. Central America may show attractive medium gold hues. It is still possible to find an 1855-S with nice original color, but such pieces are becoming increasingly hard to locate as more coins are cleaned or dipped.
EYE APPEAL: It is much easier to find an 1855-S with good eye appeal than it is an 1854-S. This is due to the fact that the average survivor tends to show less wear. Many 1855-S double eages are well struck and show above-average luster. The collector should be able to locate a nice example without much of an effort.
INTERESTING VARIETIES: All 1855-S double eagles have Slanting 5’s in the date. Most have a normal A in STATES while a smaller number have a broken crossbar on this letter.
There are a number of positional varieties and two important mintmark varieties exist.
Small S: The mintmark is placed directly over the N in TWENTY and the serifs of the mintmark are clear.
This variety appears to be scarcer than the next.
Medium S: The mintmark is positioned more to the left and it is over the left of the middle of the N in TWENTY. The top serif of the mintmark either joins or is very close to the body.
This variety appears to be far more common.
PROOFS: No Proofs of this date were struck.
HOARDS: There were 59 examples in the S.S. Republic including seven in Uncirculated. At least 63 Uncirculated pieces were included in the group of 304 recovered from the S.S. Central America. A number were included in a shipwreck found off the coast of Florida in the early 1970’s. These have noticeably granular surfaces and are likely not to be graded by PCGS or NGC.
BUYING TIPS: This is a relatively easy issue to find with good eye appeal, so the collector with a small degree of patience should be able to find a nice example for his set.
AUCTION RECORD: The auction record for this date was set in December 2000 when Christie’s sold the finest known example from the S.S. Central America, graded MS66 by PCGS, for $120,750.
FINEST KNOWN: The unquestioned finest known 1855-S double eagle is the PCGS MS66 from the S.S. Central America which sold for $120,750 as Christie’s 12/00: 90. Interestingly, this coin has not been sold at auction since its one and only appearance in 2000 and it would be interesting to see what it would bring today.
TOTAL KNOWN: 2000-2500+
Very Fine: 400-500
Extremely Fine: 800-1000
About Uncirculated: 650-800
POPULATION FIGURES: As of the beginning of 2015, the finest graded by PCGS include 15 in MS63, six in MS64, one in MS65, and one in MS66. A total of 93 have been graded in Uncirculated by PCGS. The finest seen by NGC include seven in MS62, two in MS63, and one in MS64. A total of 34 have been graded in Uncirculated by NGC. These figures are slightly inflated by resubmissions. CAC has approved one in MS60, three in MS61, one in MS62, and one in MS65 for a total of six. CAC has also approved a total of nine Uncirculated examples of varieties.
PERFORMANCE SINCE 2002: In the current market a Choice About Uncirculated example of this date (equivalent to AU55) is worth $4,000-5,000. In 2002, the same coin would have been worth $1,500-1,750. In the current market, an average quality Uncirculated example of this date (equivalent to MS61) is worth $11,000-13,000. In 2002, the same coin would have been worth $4,000-5,000.
COMMENTS: When researching this coin, potential buyers should be aware that the 1855-S tends to have a different “look” than the other Type One S mint double eagles from this era.
David Akers (1975/88)
(PCGS CoinFacts editor's note: David Akers great book on Double Eagles was written in 1982, some 20 years before the SS Central America treasure hoard came to market. The hoard contained significant quantities of 1854-S, 1855-S, 1856-S, and 1857-S $20 gold pieces. So here's what the rarity comments looked like prior to the SS Central America hoard.)
The 1855-S is a fairly scarce date that can be obtained without too much difficulty in VF or EF condition. In AU it is very scarce and in full mint state it is definitely rare. Choice or gem quality "original uncs" are virtually impossible to locate although an occasional "saltwater unc" is available. Overall, this date is on the third level of rarity among all S-Mint issues and it is roughly comparable to such dates as 1857-S, 1858-S, 1859-S and 1863-S. It is not as rare as the 1854-S but it is certainly more rare than the 1856-S.