Microsoft Hardware has a prototype Arc Touch Mouse that was never released and used for internal purposes. "Only a limited number was ever produced," revealed Brandon LeBlanc.
Brandon got the chane of hand-on the prototype, writes "The protoype Arc Touch Mouse is made with a clear plastic at the front (where the Touch strip and buttons are) where you can see all the electronics inside that power this mouse." That's right - you can see the insides of the mouse!
Brandon notes for the "bendy" part of the mouse, it too is also clear using a clear rubber material. It feels just like the same material that's on the released version of the Arc Touch Mouse but just clear. On the "bendy" section of the mouse grease is used to aid in the "bendy-ness". Because this special Arc Touch Mouse is clear, it shows a dark/black "smudge" if you look close.
Here are a couple of photos of the Arc Touch Mouse: