An AU50-graded 1792 disme in silver is expected to make in excess of $400,000 at Heritage Auctions' April 27-May 1 sale.
The lot is the finest known of the three existing specimens struck in silver.
It was ordered especially by George Washington, who is rumoured to have supplied some of his personal silver to the Mint to produce the limited issue.
Heritage comments: "In contrast to the 1792 half disme, there is little in the historical record that directly addresses the disme of the same year.
"Only three examples are known to collectors today, with two specimens struck on a normal flan and another on a thick planchet, with the date effaced.
"The present coin is by far the finest-known example, having graced the fabulous collections of Dr. J. Hewitt Judd and Donald G. Partrick."
A 1792 half disme will cross the block at Heritage's Platinum Night sale at the end of April.
An MS65-graded 1915 Panama-Pacific Exposition $50 octagonal is also selling at Heritage at the end of the month, and is valued at more than $125,000.
The coin was issued as a souvenir at the exposition and features a design by acclaimed American sculptor Robert Aitken.
Another MS65-graded specimen made $205,625 at Heritage last year.
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