It's possible I suppose. Several mfgrs used the same scheme. Prior to the advent of 1/4-inch drive, the "M" signified "Midget" and usually 9/32-inch drive. When 1/4-inch drive came along, they added the "N" (probably signifying "new") to distinguish it. As for the numbering scheme on the sockets, the "6" is the number of points, and the "06", "07", etc is the AF size of the service opening in 32/nds.
But, a New Britain hinge handle was NM-51. Williams and Armstrong hinge handles were NM-42, like the hinge handle in the Fairmount set.