Santa Fe went to containers loaded onto converted baggage car frames in the earlier 1960's, I am not for certain, but I would bet the containers were loaded by hand and then the containers were set on the cars by machine. Santa Fe's Fast Mail Express train # 7 / 8 in peak season would run 20 -25 car trains and sometime up to three sections PER DAY
The cars and containers for this service are available at N Scale Kits!
Peter Harris
N Scale Kits
www.nscalekits.com