La Casa de Moneda de México (the Mexican Mint) was established in 1535 and is the oldest mint in the Americas. Apart from manufacturing all the circulation coinage for Mexico, the mint also strikes coins in the internationally popular one ounce of silver format. The best known of these is the Libertad series of bullion coins, which has been issued in a number of sizes in gold since 1981 and in silver since 1982.
There are two Libertad silver ounce coins in this set - the "regular proof" coin, and the somewhat confusingly named "Reverse Frosted" or "Reverse Proof" variety.
The latter variety is actually "inverse frosted" - that is, the areas that are normally frosted (on both the obverse and the reverse) are mirror-like surfaces on it, and those that are normally mirror-like are frosted.