While the provided context from the search results does not contain the specific textual information needed for a detailed answer, the amount of silver in a United States dollar coin is determined entirely by its series and year of mintage. The term "silver dollar" can refer to several different coins with widely varying silver contents.
For the classic U.S. silver dollars that were intended for circulation, such as the Morgan Dollar (minted from 1878-1904 and again in 1921) and the Peace Dollar (minted from 1921-1935), the composition is standardized. These coins are made of 90% silver and 10% copper. By weight, each of these dollars contains approximately 0.7734 troy ounces of pure silver. This 90% silver standard was common for most U.S. silver coinage of the era.
A later coin, the Eisenhower Dollar (1971-1978), causes some confusion. The vast majority of these coins, which were intended for general circulation, contain no silver at all; they are composed of a copper-nickel clad alloy. However, the U.S. Mint also produced special collector's versions of the Eisenhower dollar, which were composed of 40% silver and contained approximately 0.3161 troy ounces of the precious metal.
Finally, modern U.S. coins with a one-dollar face value are typically bullion or commemorative pieces not intended for circulation. The most prominent example is the American Silver Eagle, first minted in 1986. This coin is a bullion piece whose value is tied to the spot price of silver. It is guaranteed by the U.S. government to contain one full troy ounce of 99.9% pure silver.
