I would be more concerned that there is no pen... seriously this is one of the pix that just f... your brain. There are a ton of signed Roger Waters out there and they keep getting cheaper and cheaper I would be surprised if any fogger is interested in doing them
I do not believe the pen is showing because he is holding it in the European fashion and/or also down as he does (overhand I think Seamus called it) - it is just not showing IMO. Seamus will know.