Antonio Vernucci wrote:

What amazes me is that I could not find any visible adjustment point (e.g. a
variable magnetic shunt). Evidently they were able to produce very precise
meters requiring no adjustment.

Yes, the whole key to the thing is that the number of windings is the only
thing that actually controls the sensitivity. D'Arsonval figured this out
a century and a half ago and we still use his mechanism for most meters.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."