Avometer Model 9 MK4 Circuit Diagram

Errata: It was suggested by my friend Dave that the meter movement symbol with three connections may be erroneous as it is a non-standard symbol that does not make sense today. Perhaps back in its time when this circuit was drawn by the AVO Corporation there may have been a meaning to it that escapes engineers today. It has also been suggested that the 10-kΩ resistor (R30) connecting to point A may be providing a static earth to the movement frame. If anyone has any more ideas, then feel free to contact me and I shall add it to this page.