Kikusui TOS 5051 Repair
Here you see the face separated from the body. The chrome shaft belongs to the variac for AC voltage setting. It is also used for the DC voltage setting, but in an indirect way, as the DC voltage is obtained not by rectifying the AC, but by using the AC voltage set by the variac as a setpoint for the DC voltage generator unit. The DC generator is housed in the aluminium box on the right of the picture.