Ron Guth: The 1785 Immune Columbia is a precursor to the extensive Nova Constellatio copper coinage of the same year. This conclusion is based on the fact that this reverse is shared with a 1785 Nova Constellatio copper (Crosby 3-B). When paired with the Immune Columbia obverse, this reverse shows an early state of the dies, without the heavy die rust seen on the Nova Constellatio Copper.
This rare die variety is found in both copper and silver versions. Two of the silver versions are known with a plain edge; others are known with a diagonally reeded edge.
1785 "IMMUNE COLUMBIA" on Obverse / "NOVA CONSTELLATIO" on Reverse
No Star Between CONSTELLATIO and NOVA
Star Between CONSTELLATIO and NOVA
Gold - unique
1785 "IMMUNE COLUMBIA" on Obverse / "CEORCIVS III" on Reverse
Notes: On May 9, 1843, Matthew Stickney, a coin collector who could only be called "advanced" by today's standards, visited the United States Mint and traded a 1785 "Immune Columbia" Cent overstruck on a 1775 British gold Guinea (plus some other American Colonial coins) for an 1804 Silver Dollar. Stickney claimed to have acquired the Immune Columbia from the New York bullion dealers, Beebee & Parshall, the day before. The gold Immune Columbia still resides in the National Numismatic Collection at the Smithsonian Institution and no other has ever appeared on the market. Stickney's 1804 Silver Dollar sold on April 6, 1997 for $1,815,000 as part of the Eliasberg collection and now resides in a PCGS Proof-65 holder in a private collection.
Sources and/or recommended reading (click on any active link to purchase that book):
"Walter Breen's Complete Encyclopedia of U.S. and Colonial Coins" by Walter Breen, p. 119
Auctions by Bowers and Merena, Inc., "The Walter H. Childs Collection" sale catalog, August 30, 1999, pp 110-111