I think Cantina_Dude has my response covered here
All the restraining bolts seem to still be in the archives (no idea on the exact amount made, but there's enough).
None of those in the archives are real Arriflex parts. All machined. No numbers, no screw holes, no 'real' details.
This was checked by Brandon and others who dug through the archives thoroughly.
To explain this I have two GUESSES...
1. They were machined copies made for their original purpose - lens adaptors, just not commercially made ones. Maybe made by a camera department years before ANH.
2. Lucas, or someone, said we need a prop that looks something like this (grabs lens adaptor holding it up to droid). Someone runs off and makes copies of it for props.
The Granite Earth, Galaxy's Edge, and Regal Robot restraining bolt replicas are all made from the same measurements from original props in the archives.
I hope that helps.
The Arriflex is a really cool find. I have one in my own collection.