The old manual compensators, that I know of, were basically manually controlled autotransformer style reduced voltage starters. Oil switching was used to control the arc and provide insulation in order to reduce the size of the switch.
Instead of timing circuits and magnetic contactors, the transformer taps were controlled by the operator. The faster you moved the handle the shorter the acceleration time, to the point were you could have almost no soft start at all. It was also possible to not move fast enough causing the transformer to over heat.
