Wow, ok. Definitely a Starrett back plunger indicator. Is it a press fit?!? So you have to press it in and out to adjust it? Can you still spin it inside the bezel to zero it?
Look like a fancy depth gauge for wide surfaces?
Maybe to measure the depth of something rough or pointy like a gear in relation to an adjoining surface?
Looks like a bit of effort went into it! I like the serrated edge details.
Any idea what the extra 4 holes are? Merely ’lightening’?
Or maybe they cleared bolt/screw heads?