I have acquired a geiger counter with a satisfactory number of buttons, dials and switches!
Now I only need to find some 1.5, 15 and 75 V batteries for it, or fitting switching regulators. The count indicators are basically discretely built decatrons!
Schematic is in the manual:
https://orau.org/health-physics-museum/files/library/manuals/hoffman-countmaster.pdf