I see that General Marshall was based in San Antonio at one time. I think you've got it. They may have already known about this insignia, but I didn't!
The entire thing measures 24.5" The metal tube measures 5.5" long and the diameter of the tube measures .7"
Thx for the dimensions. Two size “AA” batteries, at 0.55” diameter and 2” length each, should fit the tube nicely. A GE model 222 3 volt magnifier bulb may fit in the front of the tube, or a bulb holder that fit there may be missing. Anyway I’m 99% sure it is an illuminated pointer that used the bulb and batteries mentioned.