Sounds like a panel truck, maybe, used by Railway Express Agency (REA).
Railway Express Agency was the business structure the railroads used to transport LCL (less than carload) packaging (as the man says, like UPS and FED EX) around the country. Although the railroads could transport LCL and bundle the lading in one car, it would have been messy to have everybody show up at the freighthouse to claim a box, and there were restrictions on the railroads doing drayage in town.
The railroads found solace in the quasi-independent Railway Express Agency (a company created and jointly owned for a while by all the railroads) which did the package/box pick up, drayage, freighting between cities and final distribution. Those in-city trips required lots of panel, one-ton and one-and-a-half ton trucks to do the work.
Maybe this is one. Hurry up and buy it so we can all find out!
