I don't think he is a staff officer. There is another helmet if you look closely in the upper right corner of the Picture. So, there must be another guy sleeping in the rocks too. A staff officer wouldn't have a frayed sling. It looks like he has his CEOI in his left breast pocket. This is of course speculation on my part but I think this is one terrific legit photo of a 2d lieutenant who looks like more of a direct commission officer. He just has this "been there done that" look. JMHO.