The value of an old $100 bill is commonly determined by its age, condition, rarity, circulation and specific characteristics. For example, bills with red or gold seals are often designated as more valuable than those with green or brown seals.
There is sometimes a big difference in the worth of old bills that seem very much alike. Serial numbers might spike the value of one bill that otherwise looks exactly like another. Bills with serial numbers less than 100 and those that have a star in the sequence are quite common and, therefore, not extremely valuable
Several websites offer pricing guides and tips for evaluating old currency. These sites indicate that there are a wide variety of factors that determine what an old bill or coin is worth. When in doubt, it may be a good idea to consult a professional auction house or currency evaluator to gain better insight about the value of an antique bill. These appraisal companies offer quote forms on their websites that allows visitors to enter the information and specific details about their currency. The company assesses the bills or coins in-house and sends back a rough estimate of what the currency may be worth.