I borrowed a Greenlee round Radio Chassis punch from my buddy of 1 1/8 to cut the hole in a Leslie Combo Preamp pedal I built for Sonny's Leslie tone cabinet. They work neat!
I suppose I'd want to have 2 meters, and a switch for each, to toggle between front and back tubes , for each side.
I also ran into this set from Weber, with a choice of up to 200Ma dial, and a Voltage companion dial....Analog Bias and High Voltage Monitor Kit: https://taweber.powweb.com/store/modkits.htm#biasmeter
The weber version has a switch included.
How high is the heater supply on a Dynaco ST-70? I know on a '59 bassman, its 6.3 vac, and this lights off of a filament connection.
I know how to check and adjust my bias on my current ST-70, but I thought it's be cool to switch back and forth between the KT-66s and El-34s , and have this in place hard wired.....and mostly because it'd look cool......