I'll bet if you look at what was on the side, it may have been something like "E.W. 3100 lbs.". Or in Hotshoe's case 4115. Back in the '70's and earier, some states required that the empty weight of the vehicle be posted on the side, usually with the owners name and address. Also it had to have the words "Not For Hire" on it if it was not a commercial use vehicle. Illinois had this up to the early '70's.
I have a theory on how they came up with the numbers-The passenger car models started with the 1500 series, called the "150", then the 2100 "210 or DeLux", depending on year, then the 2600 "Fleetline or Bel Air", I think the early Impalas were the 2800. It would make sense that the next vehicle line, the trucks, would begin with the next number sequence, 3000. Or at least that my theory.
