2006 United States Silver Proof Set - 11 pc set, about 1 1/2 ounces of pure silver.. The 2006 United States Mint Silver Proof Set features proof versions of the five 2006 commemorative quarter–dollar coins in the United States Mint’s 50 State Quarters Program – honoring Nevada, Nebraska, Colorado, North Dakota and South Dakota – as well as the Roosevelt dime and the Kennedy half–dollar, all minted in lustrous 90% silver, Each of these beautiful silver proof coins has a distinctive cameo appearance created by the contrast of a finely detailed frosted foreground against a mirror–like background. The United States Mint Silver Proof Set also includes a proof version of the “Return to Monticello” nickel — the final coin in the Westward Journey Nickel Series? – as well as the Sacagawea Golden Dollar and a Lincoln cent.