I have seen three core true grounding on 201Ks, not very often but the odd one turn up now and then. The standard eventually became what they call double insulation, and were given the squre within a square mark; it's up to todays standards, and most electrical equipment from 1950 and up has it. There is a few things that might be pointed out today, on some plugs the wire ends (flat round things on the end of wires fitted to the back of the three prong socket) are half exposed, these need attention and a clever way about it should sort tings out. Most electrical equipment from 1930s and up are very close to current standards and there should be solutions to safely rewire old motors. You can't use these machines in wet rooms like the bath, or too close the kitchen sink, but the living room is fine, and in most cases the kitchen table too.