Kennedy Half Dollar
We need to add the Kennedy half dollars because 1964 was the last year they made silver half dollars. We have amazingly found quite a few of these, and even on the beach.
We can't help but wonder why people would have half dollars in their pockets at a beach. But we know why they lost them, because they are so heavy.
History: 
Gilroy
Roberts was the former chief engraver for the Mint. He designed the obverse
for this coin. His stylized initials are on the truncation of the bust of
John F Kennedy. The reverse has the presidential Coat of Arms and it was
done by engraver Frank Gasparro.
A few pieces dated 1971D and 1977D were struck in silver
clad by mistake. From 1965 to 1970 the Kennedy half dollar became a clad coin
with the outer layers made of .800 silver, .200 copper bonded to an inner core
of .210 silver and .790 copper.
Recommended books:
Handbook of United States Coins: The Official "Blue Book" by R. S. Yeoman