The provided context from the search results was not sufficient to answer the question. Based on general numismatic information, the amount of silver in a U.S. silver dollar depends entirely on the year it was minted, as the composition has changed over time.
Historically, the most common silver dollars that were circulated, such as the Morgan Dollar (minted from 1878-1921) and the Peace Dollar (minted from 1921-1935), are composed of 90% silver and 10% copper. These coins contain approximately 0.7734 troy ounces of pure silver. This 90% silver composition was the standard for most U.S. silver coinage for many decades.
Later, from 1971 to 1978, the U.S. Mint produced Eisenhower dollars. The versions intended for general circulation were made of a copper-nickel alloy and contained no silver. However, the Mint also produced special collector's editions in both uncirculated and proof conditions that were made with a 40% silver composition. These specific 40% silver Eisenhower dollars contain about 0.316 troy ounces of pure silver.
It is also important to distinguish these historical coins from modern bullion. The American Silver Eagle, first minted in 1986, is a bullion coin with a face value of one dollar. It is not intended for circulation but is valued for its precious metal content. Each American Silver Eagle contains one full troy ounce of .999 fine silver.
In summary, U.S. dollar coins minted for circulation in 1935 or earlier contain 0.7734 troy ounces of silver. Regular circulation dollars minted after that date contain no silver, with the exception of certain collector's issues.
