1966 United States Special Mint Set in Original Government Packaging With 40% Silver Kennedy! 5 Coins Inside!. The 1966 Special Mint Set contained the Kennedy Half Dollar, Washington Quarter, Roosevelt Dime, Jefferson Nickel, and Lincoln Cent although the packaging would be modified. The half dollar was struck in a composition of 40% silver. All special mint set coins for this year were struck at the San Francisco Mint. During this time, the use of mint marks had been suspended, so the coins do not contain the typical “S” mint mark. The United States Mint modified the packaging for the special mint sets. Rather than the previous cellophane and white envelopes, the coins were mounted within a rigid plastic holder with a blue background. This holder was placed within an outer blue cardboard box. Special mint set coins typically have a uniformly brilliant or proof like finish. A minority of examples will display cameo contrast with design elements frosted against a proof like background. These cameo or deep cameo examples are prized by collectors and command premiums.