Hello there! The provided context didn't include specific details about the 1964 Kennedy half dollar, but as a content expert, I can certainly explain what makes them valuable.
The most important factor that makes every 1964 Kennedy half dollar valuable is its silver content. This was the last year the half dollar was made of 90% silver. Because of this high silver content, even a common, well-worn 1964 half dollar has a base value tied to the current market price of silver, which is significantly more than its 50-cent face value.
What makes one 1964 half dollar more valuable than another comes down to a few key collector-focused details. First is the coin's condition, or grade. A coin that never circulated and remains in pristine, brilliant uncirculated condition will be worth much more to a collector than one that is scratched and worn.
Next are the special versions and rare varieties. The U.S. Mint produced special "proof" coins for collectors, which have a mirror-like finish and are typically more valuable. Among these proof coins, there is a rare and sought-after "Accented Hair" variety, where the hair strands above President Kennedy's ear are much more defined. This early design was quickly changed, making these versions scarce and highly prized. Other valuable examples include coins with minting errors, like a doubled die, where the lettering or image appears doubled.
So, in short, while all 1964 Kennedy half dollars have a solid intrinsic value from their silver, the truly high-value coins are those in exceptional condition or rare error and design varieties.
