Ron Guth: In addition to the copper-nickel "clad" Ike Dollars that were made for circulation, the Mint offered an option to collectors to purchase (at a premium, of course) Uncirculated and Proof versions made of the same 40% silver composition that had been used on the Kennedy Half Dollars from 1965-1970. The Uncirculated coins were sold individually in pliofilm packs inside blue envelopes, while the Proof versions were sold in GSA-style "slabs" inside a brown cardboard slipcase. All of the silver issues were struck at the San Francsico mint. All dates in this series are common, though the 1973-S Proof sells for a premium because it boasts the lowest mintage of the series. As with the Copper-Nickel issues, the non-Proof silver versions can be difficult to locate in top condition. The most popular variety is the so-called "Peg -Leg R of LIBERTY", which has no serifs on the left side (research continues on these interesting varieties and numerous discoveries have been made in the past few years).