I don't understand something about the coin above. It has each year and mint mark, but also has "In sets only" for each year and mint mark with a lower mintage.
What is the difference between 2002 D and 2002 D In Sets only?
You are completely right. I do not know as well. I found 2 cases of these 'In Sets only'.
Case A. There are some sets, where special dies were used to produce them. In most cases these dies are better polished. But being withdrawn from the set, the coins very soon are difficult to distinguish from circulated. Very seldom the mint use completely different dies for such sets.
Case B . There are some sets, where no special dies were used to produce them. In most cases these dies are exactly the same as used for regular coinage. These coins indeed have better look. But some sets were composed of coins from regular mintage: these coins are just packed. In this case no neediness to withdraw a coin from the set to see that it is exactly the same, with nicks and fine lines as a coin from pocket.
The best thing to do with sets: do not open them, in case B no one in the world could ever prove that a coin was from sets.
To summarize: a coin which is in a package from mint, and which was distributed in sets by Authorities is 'In Sets only'. This is the main sign, how to distinguish it from regular coin.
