There are 32 known RPM 's listed on Varietyvista.com you may wish to sit down with the coin in hand and check each known variety. Also look look at mint mark styles.
Can you photo the condition of the whole obv and rev? it screams late die state and PMD. the mm doesn't look correct for the date and it doesn't seem to match any RPM's.
Supposed to be a MMS-006. I will generate more pics as soon as I can. The closest thing to an rpm mark is on the right side big curve, I don't know that it is and will try to bring it up.
There is no inverted Mint-Mark for 1945 . As others have said, I haven't found a match for this RPM either ..