I have noticed a very interesting numismatic trend in the past few years. The coins that have shown the greatest increases in demand (and have had their prices rise accordingly) are what I term "stand alone" coins. I loosely define a stand alone coin as one whose rarity and level of interest transcends the series of which it is a part. A list of qualifications for stand alone coins includes the following criteria:
The coin is rare but not so rare that it becomes esoteric.
The appeal of the coin is widespread.
Its "essence" is easily definable--it has a great story or interesting history.
It has "cross appeal" --i.e. collectors in various series all want this particular coin.
It is affordable.
It exists in relatively high grades(s).
Stand alone coins exist in many series and range in date from the 1790's to the 1950's. What follows is a list of coins that, in my opinion, meet the criteria that I listed above. I have also included a short comment about each.
1793 Half Cent: First year of issue; one of the first U.S. coins. 1796 Half Cent: Rarest single year of issue; lowest regular issue mintage. 1793 Half Cent: First year of issue; a desirable issue for 150+ years.
1793 Liberty Cap Cent: The rarest of the three types of 1793 Cents. 1799 Cent: Rarest Large Cent and hardest to find choice. 1856 Flying Eagle Cent: Rarest and most popular small cent. 1877 Indian Cent: Rarest Indian Head Cent. 1909-S VDB Cent: Most famous US small cent; a coin every collector wanted as a kid. 1955 Double Die Cent: Best known error coin; very distinctive appearance.
1792 Half Disme: First regular issue U.S. coin; association with George Washington. 1802 Half Dime: Rarest half dime; important U.S. rarity.
1796 Dime: First year of issue. 1838-O Dime: First mintmarked issue of this denomination. 1916-D Mercury Dime: Rarest and best known coin of this design. 1942/1 P+D Dimes: Only recognized overdates in the Mercury Dime series.
1796 Quarter: First U.S. quarter dollar; one year type. 1870-CC Quarter: First Carson City quarter; earliest issue from this mint. 1916 Standing Liberty Quarter: Popular first year of issue; famous bare breast design. 1918/7-S Quarter: Rarest issue of this design; only overdated issue. 1932-D Quarter: Key issue in the newly-popular Washington Quarter series.
1794 Half Dollar: First U.S. half dollar; rare low mintage issue. 1796-97 Half Dollars: Rarest U.S. silver type (Small Eagle reverse). 1815 Half Dollar: Rarest year of the Capped Bust design. 1836 Reeded Edge Half Dollar: Popular low mintage; first Reeded Edge issue. 1839-O Half Dollar: First collectible branch mint half dollar; obverse mintmark. 1870-CC Half Dollar: First Carson City half dollar. 1921-D Half Dollar: Rarest modern half dollar.
1794 Silver Dollar: First U.S. silver dollar; very rare low mintage issue. 1836 Gobrecht Dollar: Popular short-lived design, attractive design. 1851-52 Silver Dollars: Very rare issues that exist both as originals and restrikes. 1870-CC Silver Dollar: First coin struck at the popular Carson City mint. 1889-CC Silver Dollar: Rarest Carson City Morgan dollar. 1893-S Silver Dollar: Rarest Morgan dollar. 1895 Silver Dollar: Popular proof-only(?) issue. 1921 Peace Dollar: First year of issue; one year type with High Relief design.
1855-C & 1855-D Gold Dollars: One year type coins; popular Type Two issues. 1861-D Gold Dollar: Only coin that was unquestionably struck by the Confederacy.
1796 No Stars Quarter Eagle: First issue of this denomination; one year type. 1808 Quarter Eagle: Rare and popular one year type. 1838-C Quarter Eagle: First quarter eagle from Charlotte. 1839-D & 1839-O Quarter Eagles: First quarter eagles from these mints; one year types. 1848 "CAL" Quarter Eagle: Struck from first California gold. 1856-D Quarter Eagle: Rarest issue from this mint; less than 1,000 struck. 1911-D Quarter Eagle: Rarest 20th century quarter eagle.
1854-O & 1854-D Three Dollar Gold Pieces: Only issues of this denomination from these mints. Closed 3 1873 Three Dollar Gold Piece: Affordable rarity with a mintage of 100+.
1795 Small Eagle Half Eagle: First year of issue and one of the first U.S. gold coins. 1838-C & 1838-D Half Eagles: First half eagles from these mints; one year types. 1839-C & 1839-D Half Eagles: One year type coins; only $5 Libs. with obverse mintmark. 1870-CC Half Eagle: First Carson City issue of this denomination. 1909-O Half Eagle: Only 20th century New Orleans half eagle.
1795 Small Eagle Reverse Eagle: First year of issue and one of the first U.S. gold coins. 1799 Eagle: Only affordable 18th century issue of this denomination. 1838 Eagle: First year of issue ; scarce, low mintage date. 1854-S Eagle: Earliest collectible issue from this mint. 1870-CC Eagle: First Carson City issue of this denomination. 1883-O Eagle: Lowest mintage New Orleans gold coin (800 struck). 1907 Wire Edge Eagle: Popular, low mintage, beautiful issue. 1933 Eagle: Only gold coin dated 1933 that is legal to own.
1850 Double Eagle: First collectible Double Eagle. 1854-O & 1856-O Double Eagles: Rarest Liberty Head double eagles. 1854-S Double Eagle: Along with similarly dated eagle, first collectible San Francisco coin. 1861-S Paquet Reverse Double Eagle: Popular experimental issue. 1870-CC Double Eagle: Rarest Carson City gold coin; first CC double eagle. 1907 High Relief Double Eagle: Popular, beautiful, great story; always in demand.
1893 Isabella Quarter Dollar: First modern commemorative issue; only commemmorative of this denomination. 1900 Lafayette Dollar: First commemmorative silver dollar. 1915-S Panama Pacific Exposition Round and Octagonal $50's: Largest size and value commemorative issues; low mintage and beautiful designs.
There are certainly other coins that could be placed on this list; my personal likes and dislikes definitely affected the coins that I included.
A collector who assembled a set that included nice examples of the 75 stand alone coins listed above would have a truly remarkable group that would encompass an incredible array of types and a broad range of dates.