I have to amend, a little, my reply #11 to Chan
The electrical circuit and meter are basically linear however I see that the meter scale is somewhat non-linear, probably to correct the transfer function of the CdS LDR to match EV.
The EV scale of this meter ranges from 2 (iso 100 f/5.6 and 8 second) to 18 (iso 100, f/5.6 and 1/8000)
As to whether, back in the day, they designed the scaling by trial and error , and whether the LDR CdS cells were specially made for exposure meters, I don't know.