I looked at all 72 of 1961 D RPM's. I do this for all RPM attributions. I narrowed this one down to 3 or 4 with similar characteristics. My final qualifier for confirmation is MM position in relation to the date and if the MM is rotated, how much.
It is a long & tough process with 1960's and 1961's.
"We are all flawed, some MD and some
PMD."
NYI