which 50 cent pieces are 40 silver

[LaDonovan]

That's a great question for any coin enthusiast!

Based on the information provided, the 50-cent pieces that contain 40% silver are the Kennedy Half Dollars minted between 1965 and 1970. These specific coins were made with a composition that has an outer layer of 80% silver and 20% copper bonded to an inner core of about 21% silver and 79% copper, which averages out to a total of 40% silver content.

In addition to the 1965-1970 Kennedy Half Dollars, special Bicentennial half dollars from 1976 were also struck in 40% silver for uncirculated and proof collector sets. So, if you're looking for 40% silver half dollars, your main targets are those Kennedy coins from the late 1960s.