Purpose
The United States Mint produces proof coins of many types, whether fine silver or gold, for collectors. Proof refers to the finish on the coin, which might represent the finest coins produced by the United States Mint. Fine silver proof coins can be bought directly from the United States Mint. The agency also targets investors with bullion coin production, but authorized coin dealers sell bullion coins.
Value
The value of a fine silver proof coin is based upon several factors. These include the age of the coin, its condition, the number minted and its rarity. For bullion coins, value is based on two factors: the weight of the metal -- either gold or silver -- in the coin and the prevailing market value of that commodity. The market value changes daily. The value of a bullion coin is solely based on the metal content, while a fine silver proof coin might be worth more or less than the value of its silver content.
Liquidity
Selling fine silver proof coins involves finding a buyer willing to pay fair market value. For bullion coins, the market is sustained based upon the daily price. Need money quickly? Bullion coins would provide a better option. If you have time to wait for a better return, proof coins would provide an opportunity to receive an amount above the silver's value.
Purity and Polish
Fine silver in fine silver proof coins means the content is 99.9 percent pure silver instead of sterling silver, which is 92.5 percent silver and 7.5 percent copper. Pure silver is too soft for jewelry, which is why copper is added. Bullion coins, such as the American Eagle silver bullion coin, contain 99.9 percent pure silver without the hand-polish and special treatment of a proof coin.