UPDATE:
I have added some new pictures, to my signature photo link, of the new/old "Brownie" aux trans. I still do not have a clue as to what the true MFG of the box would be. The number located on the top cover plate is a nice clean 4 digit number rather similar to what nomenclature Spicer used. Is it possible that this box could simply be an older model Spicer, Brown and Lipe or Watson? Take a look at the pictures and let me know what you think. Does anyone visit this forum from the Antique Truck Club? Maybe someone from that group will have specific information that can help to ID the aux box.
Alan