Waist width? Button?

[kresty]

Actually, I'm wrong, you can see the top of the button just barely in this picture.  Once I knew where to look it was more visible.

Make the picture really big, then look in the middle and you can just see the droid.  It was running in this photo so the button is latched to the down/hard to see position.  I cropped the bottom photo so you can see it (may need to click on photo to enlarge).

Lego Greebles of Sentry Droid

Latching Power? Button in rear of droid when running
When running the power button is hard to see, latched in the "down" position.  The white marks on the side vanish as well (I think)