Its probably a 3 compartment fuel delivery tank. It could have been on a horse drawn wagon, but it probably was on a bob tail truck. The box in back housed a meter to pump off and was used for carrying lubricants. Most of them have been destroyed and now most recyclers won't take them because they hauled leaded gasoline. If you post a picture, I can probably date it. My father went into the gasoline distributing business in the 30's and I'm still in it. Socony-Vacuum marketed under that name in the midwest in the 30's