I actually backed away from Muntz in the above post...Remembered that Hallacrafters made some 3 Knob sets...the knobs and bezel on this set seem to match beter (photofact set 92, folder 3, 4/50):
But the Knobs are
not in a straight line...
Update : Looking through my early Photofacts, I see several more 3 Knob sets from that era... Bendix, Park View and Truetone, but none of the sets pictured look much like the "mystery set". My Photofact sets are not complete, however.