1. Rarity: 1791 silver dollars are considered rare, with only about 1,758 minted. The rarity of a specific coin, such as a proof coin or an error coin, can significantly increase its value.
2. Condition: The condition of a coin is determined by its appearance, including the level of wear, scratches, and other damage. Coins in higher grades (such as those graded MS-60 or above) are more valuable than those in lower grades.
3. Certification: Coins that have been certified and graded by reputable third-party grading services, such as the Professional Coin Grading Service (PCGS) or Numismatic Guaranty Corporation (NGC), are typically worth more than uncertified coins.
Based on these factors, the value of a 1791 silver dollar can range from a few thousand dollars to tens of thousands of dollars, or even more for exceptional specimens. It is important to have the coin professionally evaluated by a numismatic expert or a reputable coin dealer to determine its exact value.