In coin collecting, the "proof coin" is a type of coin that is often sought out by collectors. They are specially created coins with higher standards and finish. The qualities are quite different than the typical circulated coin because of their reflective characteristics and construction.
So what makes a proof coin so different? A newly minted coin may not be circulated to the public, but that doesn't necessarily make the coin a proof coin. To really understand the difference, you'd want understand how the coin is made.
Proof coin construction is unlike circulated coins. The coin is forged when two dies strike and collide with the metal. The two dies have the front and back sides of the coin engraved with the coin design. Moreover, the coin is struck twice giving the design a finer detail than other coins. By striking twice, the metal is embedded more into the template of the die and allows finer lines and shapes.
The proof coin is also unique by the polish and treated die, which gives it a different appearance compared to circulated coins. The dies are applied with acid and the background of the die is polished. This gives the coin a mirror-like feel for the background and a frosted look for the other parts of the coin design.
Proof coins also have a notable distinction. The coins will typically have a letter, a mintmark, near the year embedded on the coin. The letter provides the location of where the coin was minted. Common places include P for Philadelphia or D for Denver.
In coin collecting, the grading of proofs is based on "PR" or "PF". This is not too different from the grading of other non-circulated coins. The grade could be anywhere from PR60 to PR70, where PR70 would be perfect. If the grade is lower than PR70, the grade is less perfect as it gets lower. Sometimes the grade may fall below PR60 if the coin was mishandled during the manufacturing process.
There is a variant of the proof coin called "reverse proof". Reverse proof coins are very similar to the proof coin. However the big difference is that the field (the empty space) has a frosty-like characteristic, almost like tarnished metal. The raised devices (raised images) have a mirror-like quality. It's commonly thought that only one side of the coin has the reverse proof characteristics—because the word "reverse" is often associated with the reserve side of the coin. But both sides have the reserve-proof characteristics.
Another variant of the proof are the prestige proof coins. These coins were the commemorative pieces during the 1990s, like the popular state quarter sets.
The coins do not come cheap. Depending on the year or collection, proof coins can set you back from a few bucks to thousands of dollars. It's important to assess the coin's value by consulting a professional coin collector or appraiser.
For coin collecting, proof coins should be valuable pieces in any collection. Proof coins are constructed with more precision, better materials and finer instruments. All of these provide coin collecting a trophy piece for any collector.