It sounds like you have a 1921 Peace Dollar, Kecia. It is a valuable coin, cataloging for $150 US dollars or more in problem-free, well preserved condition. 1928 is the other good date for Peace dollars, with catalog values starting at $300 in worn condition and rising to $800 in fully uncirculated condition.
Except for the 1921 and 1928 dates, the remaining coins in the Peace dollar series are generally worth their basic bullion value, plus a premium to account for buyer demand. 1922 and 1923 are the most common dates.
As the price of silver goes up, Peace dollars gain more and more value. Of course if silver runs downward, so do Peace dollars. A decent rule of thumb for common date silver dollars is to first take the price of silver (found on web sites such as kitco.com in US dollars per troy ounce), multiply it by 0.773, which is the number of troy ounces of silver in a US silver dollar, to get the base value (BV). For instance, if silver is selling at $20 per troy ounce, the base value is 0.773 x 20 = $15.46. Once you have the BV, add a collector premium to that number to get a retail value. The collector premium varies with condition, as follows:
worn: $3 US dollars added to basic silver value
average circulated: $5 added
well preserved: $10
fully uncirculated: $20
coins dated 1922 and 1923 are very common, divide the premiums by two
There are a few dates and mint marks which command higher added premiums if they are in fully uncirculated condition. These are:
1924S: add $150 to BV for fully uncirculated coins
1927D: add $120
1927S: add $120
1928S: add $120
1934D: add $100
1934S: add (are you ready?) $1200
The calculations above yield an approximate retail price. If you sell coins to a dealer, he or she will pay much less than retail in order to reserve a markup to keep the dealership solvent. You can learn about dealer markup in our discussion of 'catalog' value on our Important Terminology page (link at upper left). Typical markups for Peace dollars deduct 30 to 50 percent from the retail price of single coins. If you have a ton silver to sell, dealers will give you better deals, making up for markup percentage with sales volume.
Jacob at Great Southern Coins gave us permission to use his picture of the 1934S. It's a beauty. You have to squint to see the mint mark. Usually a magnifier is required to read it.
The key date of the Peace dollar series is 1928. Here is how catalog values run for coins dated 1928 with no mint mark:
PEACE DOLLAR 1928
worn: $250 US dollars approximate catalog value
average circulated: $350
well preserved: $380
fully uncirculated: $900
If you have a 1921 Morgan dollar instead of a 1921 Peace dollar (see this CoinQuest link), it is not valuable. It is worth about the same as a common date Peace dollar.
1921 is the year they switched from Morgan to Peace dollars, so it is the first year of issue for the latter. It turned out that the new Peace dollar design was very difficult to strike, and a lot of minting machines broke under the strain. After 1921 they changed the design by making it flatter. This means the 1921 coins are special and coin collectors love special things. The increased collector demand for 1921 Peace dollars drives the price up.
If Kecia thinks her coin might be in extra good shape, it is worth having it authenticated, graded, and encapsulated by a third party service. PCGS, ICG, ANACS, and NGC are the recognized leaders in such services. Look them up on the Internet. Do not use others.