In looking aorund the internet, I found a firm, Broad Gauge Bodies, that makes HO models of Australian freight cars, including some that are lettered differently on each side. An example is shown below: Do any of our Australian members know if such a car is available in N scale. If so, I'd be interested in finding out how to acquire one!
Umm, to tell the truth, I've never actaully noticed a 'double sider' in real life. That doesnt mean they dont exists, because you dont tend to see both sides of a car as it rattles past you at a level crossing, but I suspect I would have noticed it at some stage. I'm talking jsut for Victorian Railways here. Colonel might have more info on NSW stuff.
Disisme, guess I should have mentioned that the prototype operated on the South Australian Railways out of Adelaide. Most of their (Broad Gauge Bodies) stuff appeared to be either SAR or VR prototype.