1940 CHEVROLET TRUCK OWNER'S MANUAL
Load Capacity Chart
Gross Allowance Weights

It shows the 1940 1/2 ton truck Maximum Gross at 4400 and 4600 lbs depending on tire size used. there is a asterisk after the 4600 #

The asterisk states:
Plates as supplied with each vehicle show maximum load rating. GVWR
Deviation of tires and equipment from corresponding rating as shown restrict load capacity in accordance with table.

I assume wherever there is an asterisk on the chart, that weight number was the number that was on the data / vehicle serial number plate for its tonnage.
Note: The above info applies to 1940 trucks, http://chevy.oldcarmanualproject.com does not have a 1939 Truck owners manual posted.

If you had this "1939 Chevrolet Truck Data Book For Chevrolet Salesmen" it shows the actually plate that was used for all the series trucks.
1954 Chevrolet Truck Data Book For Chevrolet Salesmen" PHOTO attached

xfiles