MS70 would be the perfect “ideal” coin. Some coins are rare in grades MS65 to MS70, and even unheard of in MS70 grade. (The attribute “MS” stands for “mint state”.)
A newly minted proof coin is also un-circulated, however it is the way it is made that causes a difference in appearance and qualifies it as a “proof”. To understand this, let’s look at how coins are made. Coins are produced when two dies strike a blank piece of metal with tremendous force. One die is engraved with the front (obverse) design for the coin. The other die has the back (reverse) coin design on it.
A proof coin is made with a specially polished and treated die! By treating the die in a special way, the coins it produces have a different appearance. Modern technology allows the high points on the coin design to be acid treated (on the die). The background (field) design of the coin die is polished, resulting in a mirror-like look on the coin it strikes.
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