This, I seriously doubt. The sapphire in those watches was in the bearings. Or at least it was in the 1950s when my Dad was a Wyler watch rep. ;-)
But, I can see glass strengthened where those little bolts would bounce off - maybe they're made of tin. ;-) And they didn't go very deep into that board.
AFAIK, they use a process similar to case-hardening.
Or, it could be some new plastic - 1/4" lexan would probably put up with that.
Cheers! Rich