For new numismatists, there is sometimes a debate as to whether a coin is a proof coin or uncirculated.
What is a proof coin?
A proof coin is any coin that was created by the mint to be a proof coin. In the United States, proof coins are either minted at the San Francisco mint and contain an "S" mint mark, or at the West Point mint, containing a "W" mint mark. Depending on the year of mintage, though, proof coins have been struck in other mints, like Philadelphia. Generally, when the government creates proof coins, pennies, nickels, dimes, etc. are created in San Francisco and the more special bullion coins, containing the metals silver, gold, and platinum, are created at West Point. Examples of coins minted at the West Point mint is the 2017 American Eagle One Ounce Silver Coin.
What is an uncirculated coin?
An uncirculated coin is any coin minted for circulated, but has either been put aside and has never circulated, or never yet made it to circulation. An example would be if a grandparent purchased a roll of brand-new, mint state pennies in 1956 and kept them aside. Those coins would still be uncirculated. If you, today, purchased a roll of pennies and they were mint state 2017-P, for example, they would be uncirculated. But, if you went to the grocery store and used them, they would now be in circulation, therefore circulated.
How can you tell?
1. Proof coins can be circulated.
Sometimes, proof coins circulate and then become circulated coins. But, they are always considered a proof, no matter if they have been circulated. Uncirculated coins, however, are no longer uncirculated when they have been circulated.
2. Mint Mark
You can tell a proof coin for the United States based on the mint. If it has an "S" and is relatively new, it is a proof. If it has a "D," "P," or no mint mark, it is not a proof.
The luster can be a good indication. A proof coin will have high details be slightly frosted, and the lower "ground" of the coin be very shiny and lustrous.
4. PF vs MS
If you have a coin that is professionally graded by a legitimate grading service, the grade can be a good indication as to whether or not the coin is uncirculated or a proof coin. If the coin is graded MS, it means mint state and is an uncirculated coin. If the coin is graded PF, it means proof and is, as the name suggests, a proof coin.
What is worth more? Proof or Uncirculated?
On average, proof coins are worth more, but if a proof coin has been heavily circulated or the uncirculated coin is a very special coin, uncirculated coins are worth far more. As an example, the 2017 American Eagle One Ounce Uncirculated Silver Coin used above is worth less than the 2017 American Eagle One Ounce Proof Silver Coin. However, as another example, an uncirculated 1856 flying eagle cent is worth far more than a proof 2000-S Lincoln cent. They both, however, have the same face value of 1 cent. Generally speaking, though, if there is an uncirculated coin and a proof coin of the same year, same denomination, same type, and same variety, if the proof coin has not been circulated, it is worth more.