The three dollar piece was a United States coin produced from 1854 to 1889. Its value was intended to tie in with the postal system. At the time, a first class postage stamp was worth 3 cents, and such stamps were often sold in sheets of one hundred stamps. Therefore, the three-dollar piece was exactly enough money to purchase a sheet of stamps. The Treasury Department also withdrew its fractional currency issues starting in the late 1870s, of which there was a 3 cent denomination. A $3 gold coin would have helped facilitate this for those desiring gold in exchange for their 3 cent coins. Despite these potential uses, the coin was minted in small quantities (~535,000 for the entire series, the smallest amount for any series of circulating United States coins), and was never widely used in commerce. Its 1854 purchasing power would be the equivalent of $77.6 today.
Authorized by the Act of February 21, 1853, the coin was designed by James B. Longacre. The obverse depicts a representation of LIBERTY wearing a headdress of an Indian princess and the reverse a wreath of corn, cotton, and tobacco. The three-dollar piece was .900 gold and .100 copper for a total weight of 5.015 grams. It had a diameter of 20.5 mm with a reeded edge. Quantities were minted in Philadelphia each year of production, as well as in Dahlonega, New Orleans, and San Francisco in certain years. Proofs were officially recorded as being minted at Philadelphia from 1859 to 1889, and only proofs were minted in 1875 and 1876. Proofs of dates prior to 1859 are also known, including extremely rare branch-mint proofs. The total quantity of coins minted each year ranges from 2 for the 1870-S (of which only one has been confirmed to collectors) to 138,618 for the 1854. Today, any specimen has a value of at least several hundred dollars, and the most valuable is the unique 1870-S, currently (2007) valued at $4,000,000 in AU-50. This coin, part of the Harry W. Bass collection, now resides in the American Numismatic Association museum in Colorado Springs.
A 1870-S specimen would have been built into one of the cornerstones of the San Francisco Mint, although the truth about this tells an entirely different story. Its exact location was never indicated. Because, shortly after the coin was installed, it was removed from the cornerstone, to the great distress of the board. It is most likely that, due to being removed by force, the coin suffered damage as it was being removed from the cornerstone. To date, this $3 1870-S has never been recovered, and this information has been sourced from records kept at the time. Back then, the decision was made to lay the case to rest and to therefore produce a second specimen. The S character of the 1870-S was added to the cast by hand by the coiner J.B. Harmstead, resulting in the shape of the S being different to all other S’s. The cast with the S was recovered in a damaged state in 1874.
Article Source: en.wikipedia.org