2 articles were written in November 2013:

Many years ago I got my hands on an old panel meter (I think I got it from friends of my parents). It was 4.5 digit meter, with a full scale range of 20 Volts. This looked handy for using it in a power supply.

Unfortunately I found out rather soon that it wasn’t working properly. its zero point was off by a large margin, and the full scale range was reading about 2 volts less than it should. Since there was no Google back then (even no Internet access at home), it was virtually impossible to get my hands at a manual for it. And when opening it up, I found myself with 5 potentiometer for calibration…