when did they start mint coin sets
Single Proof coins were available from the Mint, at a premium over their face value, in the years in which they were minted. In 1936 the Mint started offering Proof coins in complete sets, cent, nickel, dime, quarter and half dollar. These sets originally sold for $1.87 each. In 1942 there were some Proof sets issued with two nickels. The regular composition as well as the silver.