WHAT IS IT ?

It reminds me of the Lufkin thread size circular calculators, if thats not too grand name for them (they are much simpler than this).

A possibility. There were still some odd threads around in the early-1900s, perhaps more in horology than other branches of engineering.

Another suggestion I have... clutching at straws, or dropped stitches. Something textile?. Setting pattern- (e.g. lace-) weaving looms or special knitting-machines, maybe?

No good. Short of someone coming on here and saying, "Oh, my Grandad used one of them every day for [ ... ] " , we may have to start asking specialist trades or museums selected by intelligent guess, if they recognise it.

You never know, there may even be modern electronic ISO-Metric equivalents in use as we type!

As was posted earlier, there is a much higher resolution image of the device here ... https://www.reddit.com/r/whatisthisthing/comments/bo4dhp/does_anyone_know_what_this_was_used_for/

Ches

This is fascinating. I have pondered it and realise that as it stands it does not calculate anything as there is no pointer and so there appears to be a significant piece missing such as an outer dial with possibly a window to set or read off the stamped numbers in the inner dial. The wire may act as a click stop for the outer dial. The dial may or may not behave been connected to a machine or manually set.

Yes I'm pretty sure there's at least one part missing that physically links and gives meaning to the relationship between the dials and the outer figures.

There doesn't seem to be any screw holes in the wooden box that indicate it was fixed to a machine.

Just speculating, like everyone else.