This 1959 Franklin Half Dollar has been certified by NGC to be PR-64 and would make a perfect addition to your set. 
Coin Highlights:

• Contains 0.3575 oz of Silver. 
• Graded PR-64 by NGC and encapsulated in a sealed holder to protect your investment. 
• Designed by John R. Sinnock. 
• Obverse: Depicts a profile of Ben Franklin facing right. "LIBERTY" is above Franklin’s bust with the motto "IN GOD WE TRUST" below. The date is to Franklin’s right. 
• Reverse: Depicts the Liberty Bell with the Legend above. Below is the denomination with "E Pluribus Unum" to the left of the bell. An eagle with its wings spread on is to the bell’s right. 
• This coin was struck in Philadelphia.