It's worth 50 cents.
A US Kennedy Half Dollar from 1976 is worth face value. Even if the coin is stamped 1776-1978 to commemorate the 200th birthday of the nation, it contains no real silver to increase its value.
The other part of the date is 1976. This is a bicentennial Kennedy half dollar and it's only face value.
The US did not make bicentennial pennies like they did with the quarter, half dollar, and dollar coin.
1976D Kennedy Half Dollar (Bicentennial) in uncirculated condition is worth $1.25. Circulated, it's worth 50 cents.
1976 was the 200th anniversary of the US, so that year is the BIcentennial. The centennial was in 1876.Please see the Related Question for more information.
A 1976 US half dollar is worth its face value- 50 cents.