Coming out of Europe, the coin was graded Proof-55 Cameo, but the firm added that it has no provenance.
Citing Walter Breen’s Encyclopedia of United States and Colonial Proof Coins, 1722-1989, NGC said an 1854 proof set was presented to visiting dignitaries from the German city of Bremen. Breen lists the mintage as 1+. These coins went missing at the end of World War II when the city was occupied.
NGC says it is unknown whether this coin was part of that set.
The coin is unquestionably a proof, according to Doug Winter, a well-known authority on gold coins, who consulted with NGC on it.
“This is one of the most important United States gold coins to have been discovered in some time and as far as I know it is unique in proof for the date,” Winter said.
The coin has deeply mirrored fields, frosted devices and squared rims unlike any other known 1854 gold $10. Further, it was struck from the same reverse die known to have struck proof gold $10s in the period 1840-1848, NGC reported.