1. Condition: The condition of a coin plays a significant role in determining its value. Quarters in mint state (MS) or near-mint state (MS-60 or higher) are generally more valuable than those with wear, scratches, or damage.
2. Rarity: Certain mint marks and varieties of the 1911 quarter can make it more valuable. The Philadelphia mint (no mint mark), Denver mint (D), and San Francisco mint (S) all produced quarters in 1911. The San Francisco mint produced the fewest quarters that year, making them potentially more valuable. Some 1911 quarters also have minor design variations, which can add to their rarity.
3. Demand: The value of a 1911 quarter is influenced by market demand and collector preferences. Quarters with attractive toning or unique characteristics can attract higher prices. Additionally, quarters that are part of complete date and mint mark sets or hold historical significance can be more sought after by collectors.
Without examining the specific coin and considering all the relevant factors, it is difficult to determine the exact value of a 1911 US quarter. If you have a 1911 quarter that you believe might have value, it's recommended to consult with a professional numismatist or coin dealer for an accurate appraisal.