I worked for GE in the 1990’s, as a generator and excitation specialist. I routinely worked on equipment that had been installed in the 1950s. I was at a paper mill once and a lot of the equipment the was war surplus, you could tell because it had”war emergency” nameplate values. The oldest unit I worked on was installed in the 20s. The generator controls were patented during the first world war.
Analog controls? Sycros & Servos?
Important stuff, but outside my training.