You can open the drivers door and read teh actual GVWR, as well as front and rear GAWR. I think that 11,500 pounds is a little light for a rating of a DRW E-350.
To check the GVW, you really need to take that one to a scale. Model to model, even off the same production line can change from one RV to another, but normally would be within 200 pounds.
If it is for sale at a RV dealership, ask to take it to a scale. You probably need to find a moving company and go and see the scale, ask the price. Or a recycling center might have a truck scale, or CAT certified scales at certain truck stops.
My RV has a 2734 pound cargo rating, 100 gallon fresh water tank, and has been measured at a scale within 300 pounds of it's total GVWR when ready for camping with full fuel and water.
Fred.