In general, US coins minted before 1964 are more valuable than those minted after due to the change in the composition of the coins. Before 1964, US coins were minted with a higher percentage of silver, making them more valuable as bullion. For example, a pre-1964 silver dollar contains 0.7734 troy ounces of pure silver, while a modern silver dollar only contains 0.4063 troy ounces of silver. This difference in silver content makes pre-1964 coins more valuable to collectors and investors.
Some exceptions exist to this rule, however. For example, some rare coins minted after 1964, such as the 1964 Kennedy half dollar, can be worth more than pre-1964 coins. Additionally, the condition and rarity of a coin can also affect its value, regardless of its minting date.