The three cent coin has an unusual history. It was proposed in 1851 both as a result of the decrease in postage rates from five cents to three and to answer the need for a small-denomination, easy-to-handle coin. The three cent silver featured a shield on a six sided star on the obverse and the Roman numeral III on the reverse.
The coin was composed of 75% silver and 25% copper to ensure that the coin would be considered real currency yet not worth melting down for the silver.
The coins were physically the lightest weight coins ever minted by the United States, weighing only 4/5 of a gram and with a diameter smaller than a modern dime and only slightly greater than the smallest gold dollars. The silver coins were known as "fishscales".
The term "trimes" is often used today for these coins but that was first used by the director of the United States Mint (James Ross Snowden) at the time of their production.
Starting in 1854, the three cent silver had its silver metal content raised to 90% in order to encourage circulation. The coin went through a design change at the time (three lines to border the star). A final design change occurred in 1859 due to striking problems: the number of lines bordering the star was reduced to two.
The three cent silver coin was minted from 1851 to 1873 at the Philadelphia Mint. In 1851 only, the New Orleans Mint also struck some of the silver three cent coins.
In the later years there were very small mintages and the 1873 issue was in proof state only. However, an earlier date silver three cent piece can be bought in worn condition for a relatively low price. The silver three cent piece (along with the silver dollar, the half dime, and the two cent piece) was discontinued by the Coinage Act of 1873.
Civil War era silver shortages led to widespread hoarding of all silver coins, and most one and five cent coins as well. Various alternatives were tried, including encapsulated postage and privately issued coinage.
The Treasury eventually settled on issuing fractional currency. These small denomination (1 to 50 cent) notes were never popular, as they were easy to lose and unwieldy in large amounts.
The answer to this issue was reached in 1865 with the introduction of the three cent nickel coin. This coin was composed of copper and nickel and was larger than the silver coin of the same denomination. The coin featured a Liberty head obverse and another Roman numeral 'III' reverse.
The three cent nickel was never intended as a permanent issue, only as stopgap measure until the wartime hoarding ceased. However, production of the coin continued until 1889, 16 years after the three cent silver was discontinued.
One reason often given for the discontinuation of the three cent nickel piece in 1889 is that this coin and the dime (10 cent silver coin) were identical in diameter, and hence caused confusion with the advent of mechanical vending machines. Another factor may have been that in 1883 the letter postage rate dropped to 2 cents, thus removing the justification for this coin.
The three cent nickel was only minted in Philadelphia and, except for a larger date on the 1889 pieces, had no design differences throughout its run. Over the course of the series mintage declined, and some of the dates are scarce. But, with an 1865 mintage of over eleven million, a type piece can be inexpensively obtained.
Three Cents - Silver (1851-1873)
Three Cents - Nickel (1865-1889)
Source: Wikipedia