Harold,
It could be. I bought a '49 1/2 Deluxe 5-window a couple years back that was a Union Pacific service truck and it had one in the same location. They pop up on eBay from time to time often NOS. I have a GMC Parts Book (Light-duty) 1939-1953 that has a picture of them in the Accessories section 22.0800 it shows the vertical storage like you have (PN 2233073) and also a set in a box that would go in the cab (PN 2233294).
