I have an old 1" NSK micrometer, model AB02, that was my father's. It's in excellent condition but it's off by -0.0025. I have no tooling with it so I don't know how to adjust it. There is a very small hole in the backside of the sleeve. Inside that small hole I can see metal but not slotted or anything, so I guess that's the backside of the sleeve. I'd post pics if I could find my cable for the phone. How can I zero this mic? Thanks.