It is hard to say. Based on regulations, the Ostfrontmedaille would be in second place, but many "higher ups" placed the ribbon further down the line. Being a "sew-on," the ribbon bar moves up and down like a roller-coaster so the angle on the second ribbon is not "head-on." I am familiar with the photo you posted. Yes, the other possibilities would include WWI commememoratives. If he had received other WWI combat / service awards, they woud have appeared on your Rangliste. The ribbons towards the end of his bar seem to be lighter colors, so the Austrian and Hungarian commemoratives would seem logical. His WWII service included Army Group Central and Army Group South, did it not? Perhaps he received a couple of Romanian awards like the Crown Order and/or the Crusade medal. Where would I look to research this possibility?