Carried on a secret mission to the Middle East by Edmund Robert, a sea trader and emissary for US President Andrew Jackson, the rare coin was a present for the Sultan of Muscat - now Oman - after a new trade treaty was ratified, allowing America into markets previously dominated by European powers.
The Sultan of Muscat coin, known to collectors as one of the "King of US coins," was one of eight silver dollars minted in 1834. The coin is dated 1804 because silver dollars were not being minted at the time and an old coin mould had to be used.
"To coin collectors this is like the Mona Lisa or the Holy Grail," said Q David Bowers, chairman of Auctions by Bowers and Merena, which conducted the sale at the Park Lane Hotel in Manhattan. The coin last sold in 1945 for $5,000.
Another 1804 coin was sold by Bowers and Merena in 1997 to a West Coast coin dealer for a record $1.8m. "If the calls we are getting are any indication, we expect to top that bid," Mr Bowers said.
"The Sultan of Muscat coin is virtually in the same condition as the day it was minted," he said. "It's never been mishandled or dropped. It's never been cleaned or polished; for that to happen over a period of 150 years is truly amazing."
Because it has never been cleaned, the coin has acquired a soft blue and gold patina over its true silver colour. It has been kept in a velvet- lined drawer in a wooden cabinet inside a bank.
A shotgun that belonged to the Marquess of Ripon, considered one of the greatest shots of all time, fetched pounds 40,000 at Sotheby's yesterday.
When the peer died in 1923, reputedly with gun in hand after bagging 51 grouse, he had recorded 556,813 head of game - an unequalled tally.
On one occasion he was reported to have had seven dead pheasants in the air at once and was also recorded as killing 28 birds in one minute.
In his life, he accounted for nearly 250,000 pheasants at his Yorkshire estate, Studley Royal, and other leading estates. On one day alone, 6 December 1905, he and friends bagged 1,078 pheasants, 65 hares, 30 rabbits and 16 partridges.