.303 Marked Gauge Tool... identity?

[Surpmil]

I would hazard a guess that this gauge was used on cases which had not yet had their necks formed.

It might have been used to gauge or at least monitor several features of the case at the same time, but perhaps the height of the anvil in the primer pocket, the centering of the pocket or even the protrusion of the primer if those were inserted before the case was necked?

Time to dig out the old TBSA 1929 I suppose.

What is scratched into it?