I can’t say that I know for sure. With the coins in hand it would be much easier to compare details such as the upper serif on the D in UNITED, etc.
I don't know about @C-B-D, but I'd be willing to send you my coin for an in-hand examination to see if this is a new variety. Or @C-B-D could send his to me and I will get them to Bill Fivaz. My initial thought on my coin was MD, but seeing such a similar coin makes me unsure now.
TypeCoin971793, posted: 2944831, member: 78244"]Check out the reverse on mine. It is exactly the same,...but it is a different year (1864)." That's the way "discoveries" happen. There are many times when a reverse die was carried over to following years or Proof dies were used for business strike coins. However, while I see a similarity between the reverse images I don't see an exact match. I hope it is just the lighting.
Just a thought. The person that should take a look is Kevin Flynn. Or you could get a copy of his book and look for a match with what he already shows.