I believe this is a 9X1 Postmaster Provisional and it has the requisite ACM initials (very faint).

In trying to compare it from what I see on auction sites, this copy appears either dark or dirty (however, I believe there were different paper used for some copies.)
I had a dealer look at this a number of years ago and his initial thought was that it was genuine, but might have been repaired(?) ... in any case, as they say, "it is what it is."
It was a gift to me by a friend who had a deceased relative who was into stamp collecting, so I have no idea as to how it was initially acquired to know any other history behind it.
Any comments would be appreciated. Thanks.