Okay, what will I be talking about today? Well, this mistake is one of those an experienced collector shouldn't make, like when the dealer at your LCS calls cents 'pennies'. This mistake may not be caught by many, but it bothers me as much as what I just mentioned. Alright, so what is this mistake? I'll start explaining it.

The Philidelphia Mint was established as the FIRST US Mint in 1792. Because of this status, it did not have to use a mintmark at all, even when Charlotte, Dahlonega, and New Orleans had mints. Philly first put its mintmark on coinage in 1979, on the SBA dollar in particular. In 1980, Philly put its mintmark on all the denominations struck there on all but the cent, which has had the P mintmark only in 2017. If you don't understand it still, then I will explain it. I have seen many experienced numismatists who will add a 'P' after a coin without that mintmark, but struck at Philadelphia. I am not sure why they would do this, but this is the mistake I will be talking about. 

Here are the reasons you shouldn't describe any denomination with a 'P' after the date if it doesn't have that mintmark.

1. Would you say "1938-D" after a coins description to indicate it was struck at Denver? Partially that, buy mostly you would add the 'D' to signify that mintmark on the coin. So saying "1938-P" would only be to say it was struck at Philadelphia, because a 'P' mintmark would not be on any coin from that year. Essentially, since there is no mintmark on many coins struck at Philadelphia, putting a 'P' after the date can only cause confusion. The Red Book lists a mintmark after the date on every coin with, but Philadelphia coins that don't have mintmarks do not appear with a mintmark after the date. So basically, by putting that 'P' there only causes confusion.

2. From 1965 through 1967, a 'punishing' of numismatists happened, due to a coin shortage mostly caused by non-collectors who hoarded popular coins such as the JFK half. Any coin dated from 1965 through '67 had no mintmark, despite many being struck at Denver. So if you were to describe a US coin as "1965-P" because it is no mintmark, so probably struck at Philly, right? Wrong. At least half of those were struck at Denver, meaning to describe a US coin as "1965-P" would have no purpose, neither to signify it was struck at Philadelphia, since it could have been struck at Denver. Nor would it be to say there was a 'P' mintmark on the coin.

So if you are an experienced collector, don't do this. Here are some ways you could describe a US coin struck at Philadelphia without that 'P'.

1. You can always do the 'P' in parentheses such as this. 1886-(P)

2. You can simply state 'Philadelphia' after the date such as this. 1962 Philadelphia

Never state a US coin as 'P' or 'D' if it is dated 1965, 1966, or 1967, as it is impossible to say.

SOURCES:
Yeoman, R. S. A Guide Book of United States Coins 75th Edition(2022)