Where a mark survives, and where it does not
The bead bodies are the worst place for a mark: they pass through the hand thousands of times a day and any surface treatment there is temporary. The imam, the separator discs and cast metal furniture are the surfaces that last, because they are held rather than rolled.
We will show you this on a physical sample rather than argue about it. A proof that has been handled for a week settles the question faster than any specification discussion.