The United States has several coins and banknotes which were proposed at one time but never adopted.

Banknotes

A three dollar bill was proposed two times during the 1860s. A design was engraved for a potential $3 United States Note, and a 1865 law called for a $3 National Bank Note, but neither proposal came to fruition.

Denomination	Obverse	Reverse	Notes
$3 note			Not to be confused with fake or privately issued obsolete notes or the three-dollar Continental currency banknotes issued during the American Revolution

Coinage

There have been several United States coins which were proposed but never adopted. Most of the coins listed below, although never adopted, were produced in limited numbers as patterns.

Denomination	Obverse	Reverse	Weight	Diameter	Material	Edge	Minted	Notes
Silver center cent 1¢			4.48 g	24.00 mm	Cu (ring) Ag (plug)	reeded	1792	The first and only US bi-metallic coin until the 2000 Library of Congress ten dollar coin.
Ring cent 1¢			various weights		90% Cu 10% Agα	various	1850–1851, 1853β, 1884–1885	196 ring cents (originals and restrikes) are known to exist.[1] Examples exist with or without a hole.
Aluminum cent 1¢			0.937 g	19.05 mm	96% Al 4% trace metals	plain	1973–1975
Two-cent billon 2¢			3.84 g	~13.00 mm	90% Cu 10% Ag	plain	1836
Two and a half cent piece 2.5¢			unknown	unknown	unknown	unknown	never minted	Proposed in 1916 by US mint director Robert W. Woolley.[2] Civil War tokens of this denomination exist.
Three-cent bronze 3¢			10.89 g	28.57 mm	95% Cu 5% Zn	plain	1863
Ring nickel 5¢						plain	1884–1885	[3][4]
Gold ring half dollar 50¢							1852	[5]
Gold ring dollar $1							1849, 1852	[6][7]
Two dollar piece $2			unknown	unknown	unknown	unknown	never minted	Proposed but not minted.[8] Some privately struck renditions exist.[9]
Stella $4			7.00 g	22 mm	6.00g Au 0.30g Ag 0.70g Cu	reeded	1879–1880
Half-union $50			83.58 g	50.80 mm	90% Au 10% Cuγ	reeded	1877	Commemorative coins of this denomination were issued in 1915. Several bullion coins are produced in this denomination.
Union $100			unknown	unknown	90% Au 10% Cu	unknown	never minted	Canceled before any patterns could be minted (fantasy coin shown). Some commemorative and bullion coins are minted in this denomination.

Notes

^α Pattern coins for the ring cent were struck in various metals, including copper, aluminum, and nickel, as well as billon.

^β 1853 ring cents are restrikes dated 1850, although they can be distinguished from the original 1850 cents in that they use a different reverse design.

^γ Although circulation strikes of the Half Union were to be 90% gold 10% copper, only two of the twenty known pattern coins were struck with this composition. The other 18 were struck in 100% copper, although some were later plated with gold by the mint.^[10]

References