The 1964 Kennedy Half Dollar is one of the most popular half dollar coins of all time. Its beautiful design can be attributed to chief engraver Gilroy Roberts, who designed the obverse of the coin, and Fran Gasparro, who designed the reverse. Gilroy Roberts served as the chief engraver of the U.S. Mint from 1948-1964 and thereafter Frank Gasparro was named as Gilroy's replacement in 1965. The obverse of the Kennedy Half Dollar features a bust of President JFK himself and the reverse features the presidential coat of arms. Collectors and investors alike favor the 1964 Kennedy Half Dollar over sequential years because it was the only year that was struck in 90% silver. From 1965-1970 the Kennedy Half Dollar was struck in 40% silver and after 1970 all silver content was eliminated from the mint state version of the piece. The 1964 in particular was minted at two different mint locations, the Denver and Philadelphia mint. Many collectors often try and find the Denver mint mark Kennedy Half Dollars because the mintage is much lower. A total of 273,304,004 Kennedy Half Dollars were minted at the Philadelphia mint, while only 156,205,446 were minted at the Denver mint. This makes the Denver Kennedy Half Dollar about twice as rare as the Philadelphia counterpart. Furthermore, there was also a proof version of the Kennedy Half Dollar that was made in 1964. The proof version had a much lower mintage than the mint state Kennedy of only 3,950,762 and was also struck in 90% silver. Collectors and investors typically buy these coins in rolls of 20 or put together complete sets in Dansco books.