It sure looks like one but to be 100% sure here the Coneca list it has all date 63-D is were it ends.:thumb: http://varietyvista.com/Variety Master Listings/franklin rpms.htm#_1963-D
Is there also doubling on the letters above? It resembles md. If the letters have md, I would say it isn't an RPM.
Seems like machine doubling. I may be mistaken, but I think it could be possible that when the MM was being punched in by hand, the ' MM stamp' slipped a bit on the way into the die and may have caused this, and there might be a name for this. Could be mistaken. No premium either way.