Dave,
As always, thanks for the comment, but take a closer look. The genius thing about this tool is that the designer substituted a large diameter bearing ball for an angle specific truncated cone insert. The same tool without the ball is used for headspace, with the ball, assuming that you are cutting the correct angle, the large ball will land on the cone (once the headspace gauge is removed from the chamber), and let the smith make cone depth comparisons, using the same ball for all cone angles.
Butch,
Your index lines for accurately transferring lettering locations is a really good touch. It seems that someone could make simple nuts, marked the same way to use with the tool that I put up a link for.
Boyd