The sides may be original. The ad calls it a 1987, not 1978 like the title of this thread, which makes sense. At some point in the 80’s, Vesley Manufacturing went out of business and somebody bought the Apache brand and the later ones were a little different than the originals, hence the different roof and possibly the walls, though it is also possible they were rebuilt. You could ask in the Apache Camper Preservation Society group on Facebook and get a definitive answer. They know their stuff.