In my humble opinion, it's too soon to say with confidence that the hull shows impressions of the ribband and damascus pattern. The striations seen on the hull could be scratches that are from the shell being removed from the barrel. Because the hull is also ruptured, it could have required turning the case while manually extracting it from the barrel. The way the hull is positioned in the picture is not necessarily how it was at the time of the failure. The owner may not have any idea if the case was removed and then reinserted in a different orientation, since the gun was out of his possession for several days. Only after close examination by an expert will we be sure.