U.S. 2018 Silver Proof Set. Unlike the regular 2018 clad proof set, this special set features seven 90% silver issues. Included with that precious silver content are the year's America the Beautiful commemorative quarters, as well as a silver Roosevelt dime and Kennedy half dollar. The set also contains a Lincoln cent, Jefferson nickel and Jim Thorpe Native American Dollar. This offical U.S. Mint set is not only desirable due to the precious silver content, but also for its expected limited mintage. Silver proof set outputs are always far below the regular proof set's production numbers.