Proof sets are the highest level of collector quality the United States Mint produces. These special silver proof coins contain 90% silver:
Never touched by human hands, these coins are real currency of the finest quality produced by the United States Mint - much higher quality than coins you'll get in circulation. Specially minted to deliver the ultimate detail with a mirror like background, they are works of art struck in 90% silver.
This 90% silver set includes:

Some coins in this special-edition set are struck in 90% silver. This is called "coin silver" because until 1964, the half-dollar, quarter and dime were struck in 90% silver. The United States Mint continues this tradition in this exclusive set.
Artwork is digitally mastered capturing the finest artistic detail of America’s natural and historic landmarks.
Dies are specially polished to provide a mirror like finish and the designs are laser frosted to create a cameo appearance.
Double struck for crisp-relief on the designs, giving them a level of detail found only in proof coins.
Never touched by human hands, these coins go right from the United States Mint into the protective package to ensure the highest quality possible.
Special packaging to showcase and preserve the finish.
These proof coins bear the "S" (United States Mint at San Francisco) mint mark.