I'd go for that. If so, then it would be one of the sought-after German ground pontils usually associated with the Greiner family.
I think some of our terminology is confusing. As I understand it >>
"Fire-polished" is today mostly associated with contemporary marble makers, I think. It essentially obliterates any trace of a pontil. Is this right, Migbar? If you're around?
"Melted pontil" is associated with the American marbles produced by Harvey Leighton in several locations (Navarre, Barberton, etc.), and you can generally see that heat has been applied to the cut-off point of a marble, enough to make the roughened glass "sink" back into the body of the marble. It can look like a very low smooth wart; sometimes there is carbon "staining" around it.
I doubt if any marble pontils either here or in Germany were ground, then polished (reheated). Not worth the cost of the process, By the 1880s or so, the German makers seemed to have stopped even grinding their pontils, for economic reasons . . .