MG Number Plane

[ginamod]

Hi All Experts,

on American Browning MGs , WWII, there are laterally engraved nummers
which lead to the plane, where they had been mounted.
I met another MG, WWII, there are no engraved numbers to be found on one of both sides, laterally (cheeks), but on the brass socket there is a number, not engraved but raised:

M(X)? - 749-927-1
9

Could this be the number that leads to the plane which had carried this MG?

All hints are welcome. Thx a lot

dnalor