All Peace dollars contain .77344oz of pure silver.
There were no dollar coins minted in 1992.
Even in uncirculated condition, 1922 is such a common date for Peace dollars that the value is primarily for the silver content. As of 1 February 2013, it's worth just over $24.
Peace dollars were made from 1921 to 1935. An 1879 silver dollar is called a Morgan dollar after its designer George T. Morgan. There's more information at the Related Question
1924 would make it a Peace dollar, not a Morgan. It's also not a rare date, so the value is mainly for its silver content. At present, a '24 or '24-D dollar is worth $22 to $30 depending on condition, while a '24-S is worth a bit more.
The last Morgan dollars were minted in 1921. The Peace design was introduced in December of that year, so any silver $1 coin dated 1922 would be a Peace dollar, just as it says on the coin's back side. The last Morgan silver dollars were minted in 1921. Your coin is called a Peace dollar. A 1922 peace dollar that was made at Philadelphia in circulated condition is worth an average of $25. This reflects the silver content. If it shows significant wear it won't be worth much more than that. If it is uncirculated they are worth up to $900 depending on quality.
There are no 1971 peace silver dollars. A circulated 1971 Eisenhower dollar is worth about $2. An uncirculated one is worth about $5. A silver collectors edition (with an "S" mintmark above the date) is worth about $10.
Because of the silver content in the dime, quarter(s) and half dollar.
The most two most valuable are the 1903-O Morgan and 1928 Peace dollar, followed by the '21 Peace and the '02-S and '03-S Morgans.
It's simple. A 1922 S silver dollar will have a S mintmark while a 1922 D silver ill have a D mintmark. The mintmark is located on the reserve below the word "ONE".
A date is also needed, post new question.
Your 1928 eagle silver dollar is actually a 1928 PEACE dollar, the first Silver Eagle bullion coin was made in 1986. But for this year of issue Peace dollar it's very important to see if there is a mintmark (S) on the reverse just above the eagles tail it makes a big difference in value. If you see the S a low value for the coin is $16.00 no S low value is $250.00. Take it to a dealer or collector for an assessment
As of 09/2008 a 1925-S Peace dollar is worth $15 to $23 depending on how much wear it has.