Thanks for the heads up on Carlos, I will try to see what he can tell me. As far as the dual format back, I had heard rumors floating around about that possibility but never really gave it much credence. I had originally ordered this one just for the holders and a back that I could use the pistol grip with When I got it and started checking it out I couldn't figure out why it had a felt light seal at the top. I was surprised as all get out when I pulled the dark slid back out. Here are a couple of shots notice in the second one the tabs that are absent from the other back in the shot.

this is the actual auction and you can see the red felt at the top of the back.