What’s the tightest tolerance you’ve actually held in production on a VMC?

Curious what people here (especially in USA/Canada) are actually achieving in production - i.e. not lab conditions.

What’s the tightest dimensional tolerance and surface finish you’ve held on a mold or die job fresh off the mill?

Anyone working in the sub-tenth/sub-micron range? If so:

1. What size parts?
2. What materials?
3. What kind of machine/process?

I’ve been digging into this space and expected to see more of it in North America, but most of what I come across seems to be coming out of Germany, Taiwan, or Japan—especially on optics-type work.

Would be good to understand what’s actually being done here.