If you want to dissect and anatomical analysis of old electronics parts , its virtually impossible. Only you can do is to buy several famous lightmeters , disassemble it , look for the light sensor part number , find it at old factory manuals , look for the electronic circuit ....and list goes on.
You have to know that they bought what is available from catalogs , test them approximately and try to be sure part would be available next few years and cheap.
They were not NASA and not sending man on to the moon.
There was no such technology at consumer goods and thats why we hate digital cameras and modern lenses even today
But Leica was always different from Gossen and others.