And made a greebly for the top to mimic the precision screwdriver. It would be interesting to hear of any further discovery or information coming to light on what vintage screwdriver of the time it might have been.
So, yeah - the 3D model and print that I ended up with on mine was made from reference to on-site Tikal shoot photos of what I'm 99% sure was the greeblie on the top of the scanner. At the time of the photos, this 'thing' was tucked into a gap on the side of the Arriflex. I can't share the photos (they are pretty soft focus anyway) as they come from a first-hand source from whom I do not have explicit permission to share, but I'm still trying to track it all down. I doubt those on the shoot will remember so small and inconsequential a detail 46.5 years later so it'll be up to us to try to track it once I can get a few more and more crisply-focused images of this thing...
Dan