1965-1970 Kennedy half dollars are 40% silver with a value of about $2.00 for the silver.
It was the Franklin half, before that walking liberty, and before that various portraits of Miss Liberty.
Remember that the eagle is considered to be one of the national symbols of the US. The design on the back of the coin is an adaptation of the Presidential Seal.
It's just 50 cents, spend it.
The US Mint has not issued a 1964 half dollar depicting Lyndon Johnson.