I really wish that everyone would stop calling the build tag #'s a VIN #, there were no VIN #'s Prior to the mid 1950's. Vehicle's were registered with either the build tag #'s and Letters or the engine serial # depending on the state. Some states even generated a small metal tag which was affixed to the vehicle at the time of registered.
I fully agree with you. VIN is government stuff, the serial number/ build tag or what ever is factory stuff. They were not forced to do it then, as is more obvious with the older trucks that had no plates.
Put it simply there was and is no VIN on a TF or older truck, well and yes none on any up to vin inception, that is unless some state put one on. And that would instantly make that truck worthless to a collector, parts only deal then.