There are certain elements that can be accepted that these coins must have.
They are calling them coins, so that's an immediate Y in the road. And also they are in the category of American Eagle Coins.
So legally, this must all be in place:
"The Act specified that the coins would have a diameter of 40.6 mm, weight of 31.103 grams (one troy ounce), and composition of .999 fine silver. The obverse design was to be symbolic of Liberty, while the reverse would contain an eagle. Required inscriptions included the words "LIBERTY", "IN GOD WE TRUST", "UNITED STATES OF AMERICA", "1 OZ. FINE SILVER", "E PLURIBUS UNUM", and "ONE DOLLAR"."
So they really can't remove any of what's there. Liberty had to be portrayed, and there had to be an eagle, although they could put a different or smaller eagle on the reverse. They could definitely modify it.
I'm not sure what exactly the Mint can do without authorization.
I know there was legislation involved in making the lettered edge in 2016, could they just have something on a lettered edge system as "ARMY 250TH ANNIVERSARY"? Possibly, but the last time they did lettered edge it was only at West Point and I also heard didn't go all that well, a lot were destroyed.
I mainly wanted to share what the reply was. I'm not suggesting "everyone here", but if a few people wanted to make independent inquiries with the mint, someone else might give you a different answer. But this is what the rep said, where I was expecting a little closer to a non answer, rather than what was said.
The codes rarely make sense, and that's what drove me to ask them. It seems too coincidental.
One code that makes sense are the Women's Quarter program, where it's the year, then WO, then the issue number for the year, like 25WO1, 25W02, etc.
You also have a longer code for dollar releases where they are in differing amounts like rolls and bags.
But for the silver eagle yearly releases, typically it's the 2 digit year and 2 digit for the product, 25EA, 25EM, 25RF, etc. The only complication was 2021 where they had the old codes, then for the type 2 they added N to the back, I've always assumed for "New" design.
Going way back, the mint didn't seem to refer to the codes at all. They possibly existed, but before the mint had a website, who knows if the referred to codes or not. Maybe on old invoices it would refer to them.
I know I tried on my own data material I try to refer to codes when I knew them. You started seeing really nonsensical codes starting I want to say about (year) 2000, them they seemed to standardize the codes, possibly about 2015 or so (the 4 digit codes).
So it does make sense that they are using a special 5 digit codes for these 3. Definitely the A,N, and M make sense, leaving us to wonder about the PM. So setting the answer I received aside, could the PM have no meaning, just (suspiciously) random, or could it have another meaning? P for Proof? M for Military? Privy Mark makes more sense. But they told me no!