In article ,
David Nebenzahl wrote:

I have an old galvanometer (nice Weston in a slant-front black crackle
case). Its scale reads 30-0-30. What units are these? Or are they just
relative values for comparison?

With a standard alkaline cell and starting with a *very high* resistance
(5 megohms, say), drop the resistance until you get a decent deflection.
Then measure the resistance and the voltage, and do the math.

Isaac