The marks looked somewhat familiar to me, so this morning I showed the picture to the body shop gurus at my son-in-law's truck shop. Two of them almost immediately said, "Yeah, that looks a lot like the scratches we fixed when [regular customer] swung his motorhome into the fence at [a local RV/boat storage yard]." That storage yard has a large mesh wire fence (a guess, about 5-6" squares) around it, and I can see how swinging the rear end into the fence between the posts would make similar marks. The flexibility of the fencing would also allow it to contour to the coach shape.