@DAM 79
Just in case you're not aware, you need to replace the thin foam layer that the mic is resting on.
I see that the thin foam is deteriorated and, in that condition, it will promote corrosion and damage the metal surfaces in contact.
That is a common problem with vintage Mitutoyo. The form fitting thicker layer seems to hold up well, but the thin layers deteriorate.
I hope the newer Mitutoyo packaging has the chemistry improved, but I don't know.
Originally, there was a thin layer in the top of the box also.
I bought a replacement foam at a craft store. It's a closed cell material, about 3/16 thick. It comes in many colors and easily available on Amazon in 2mm. Just build up layers to get the thickness you need.