Each of the mints that produce U.S. coins have long put a letter, or mint mark, on their coins to indicate to the public and to collectors where those particular coins were made.
While current production comes from three mints – Philadelphia, San Francisco, and Denver, and West Point there were previously minting facilities in:
Carson City, Nevada
Charlotte, North Carolina
New Orleans, Louisiana
All of these locations have always used mint marks on their coins, though the Philadelphia mint traditionally did not. Collectors generally knew that any coins that did not have a mint mark were produced at the Philadelphia mint. An exception was Jefferson nickels produced there from 1942-1945; those did have a fairly large “P” on the reverse side of the coin. Another exception was the 1979 Susan B. Anthony Dollar.
Since 1980, coins produced at the Philadelphia mint have had a “P” mint mark, with the odd exception of the penny. For whatever reason, that coin, and that coin alone, did not have a mark.
That’s going to change in 2017, as the Philadelphia mint is celebrating its 225th anniversary. As part of that celebration, the mint is using the “P” mark on all of its coins, including the cent.
Ordinarily, collectors would rush out to buy these pennies, and chances are that many people are hoarding at least a few. After all, the mint has announced that this is a one-off aberration, and that in 2018, we’ll likely see pennies coming from Philadelphia that lack a mint mark again.
That sounds like a great opportunity for the opportunistic, with just one problem – the 2017 pennies being produced at the Philadelphia mint aren’t rare. In fact, they’re quite common, as the mint has produced nearly two billion of them through the end of May, 2017. At that rate, there might be 4-5 billion of them in circulation by the end of the year.
It’s times like these that the oddities may turn up. Perhaps the mint has (or will) accidentally produce a few cents that lack a mint mark. In this case, as with the 1944 steel penny, it’s the exception that generates the appeal among collectors.