Starting from most recent silver half dollar coin to oldest:

Kennedy silver half dollar coin 1964-1970
Franklin silver half dollar coin 1948-1963
Walking Liberty silver half dollar coin 1916-1947
Barber silver half dollar coin 1892-1915
Seated Liberty silver half dollar coin 1839-1891
Capped Bust silver half dollar coin 1807-1839
Draped Bust silver half dollar coin 1796-1807
Flowing hair silver half dollar coin 1794-1795

The Kennedy half dollar coin is made of 40% silver between the years 1965-1970. The 1964 model is 90% silver.

The most important thing to note from a precious metals value standpoint requires that we go back to 1796 with the Draped Bust silver half dollar coin.

The coin actually didn’t have a face value associated with it. The coin was literally valued in terms of silver and the ideology behind the US Mint producing the coin was simply market recognition for users to know the coin was made of silver.

One simply identified the silver coin denominations at the time by their size. It was common sense and more silver simply meant more value and buying power.

As the concept of the face value became utilized in the centuries to come, our society allowed the elimination of any form of gold standard or “backed by” value with the dollar. Having a currency only valued by it’s acceptance in society as a medium of exchange is known as a fiat currency. A copper coin, in this case, the half dollar coin, eventually took over because it could be minted for less cost than the face value.