These are some photographs of my Dad's voltmeter (click the pictures for the full size versions). The lower switch sets one of 6 ranges and is labeled (top left to bottom right) S, R, 550V, 270V, 94V, 9V. The upper knob allows calibration of the resistance range. The resistance range uses 3 standard 1.5 volt AA size batteries, rolled into a paper tube and pressed between two screws on a small block of wood. On the paper tube the dates of battery changes are written. The last change occured in 1985.