The coin you are referring to as the "1979 liberty dollar" is formally known as the Susan B. Anthony dollar. Its value is determined by several factors, primarily its mint mark, its physical condition or grade, and whether it is a rare variety.
For the majority of 1979 Susan B. Anthony dollars found in circulation, their value is simply their face value of one dollar. These coins were produced in very large quantities at the Philadelphia (P), Denver (D), and San Francisco (S) mints and are considered common.
However, the value can increase for coins in pristine, uncirculated condition. A standard uncirculated 1979 dollar from any of the three mints might be worth between $2 and $5. Coins that have been professionally graded and are in a very high mint state can command prices of $20 or more.
The most significant factor for a higher value is a specific die variety known as the "Wide Rim" or "Near Date" 1979-P dollar. On this scarcer version, the rim of the coin is thicker, and the date appears much closer to the edge than on the common "Narrow Rim" variety. A 1979-P Wide Rim dollar is a sought-after collectible and can be worth anywhere from $30 in circulated condition to several hundred dollars or more in a high-grade uncirculated state. To determine an exact value, the coin would need to be examined by a professional coin dealer or a third-party grading service.
