A fantastic example of the 1804 silver dollar has sold at the top of Heritage Auctions' August 8-10 US Coins Signature Auction in Rosemont, Illinois.

The 1804 silver dollar were actually minted in the 1830s as part of special proof sets produced for Asian dignitaries

The coin, one of the rarest of all US silver pieces, sold for $3.8m, topping the $3.7m seen by another PR62-graded example at Heritage Auctions in 2008.

Prior to the 2008 sale, another example had not been seen at auction since 2000. There are just eight Class I specimens known to exist, three of which are in institutional collections.

Despite its dating, the coin was actually one of a very limited production from the 1830s.

The US Mint records that 19,750 silver dollars were minted in 1804. However, all of these were struck from the same dies used for the 1803 minting, and therefore still bear the previous year's date.

A silver dollar bearing the 1804 date did not appear until 1834, when the US department of state created a set of coins to present to Asian rulers in exchange for trade benefits.

The sets were to include two specimens of each kind of coin still in use, including the 1804 dollar, so mint employees were obliged to produce a few examples to cater for the demand.

These are known as Class I specimens, and are the only 1804 dollars that were legally produced.

The example at auction originates from the Greensboro Collection, a remarkable amassment of proof coins that Heritage has been involved in the sale of since October 2012.

The record-holding Watters-Childs specimen is one of the most valuable of all US coins

Between 1858 and 1860, Mint employee Theodore Eckfeldt illegally struck a small number of the coins and sold them to collectors. Most of these Class II and Class III examples were seized, however a few escaped and remain on the market, with the Adams-Carter specimen selling for $2.3m at Heritage in 2009.

The highest-graded example of the 1804 dollar is the Watters-Childs specimen at PR-68, which sold for $4.1m in 1999 to set the record for a coin of its type. It is believed to have originated from the Sultan of Muscat's proof set.

In September, Bonhams will sell the Tacasyl Collection of Magnificent United States Proof Gold Coins, starring the famed $4 Stellas.

See our superb selection of rare coins for sale for the latest addition to your collection.