A lot of the old machine are up to todays standards, I'm pretty sure of it. They need a bit of work and clever tweaks to be good as new, and they can be rewired to a good standard. Not all can, and a lot of the early electrics didn't have good enough insulation. I just can't see a big difference in the new motor setups we can buy as replacements, and the old ones, the pulgs are different, but not necessarily worse or better. A lot of the new pedal replacement we can buy are exactly the same as the old, they are not all electronic or solid state, basic carbon resistors. There are 201 with earthed wiring, and most of the 1950s machine are double insulated.
Roger posted a picture of a 201 with a common type of plug where the wire ends on the back side looks like they are not fully insulated, but all plugs weren't like that. By 1950s the standard were often better than what we get today, some wirings and electrics are very light weight and cost effective today. I should get a residual current detector like yours DalronAU to make sure nothing is wrong. These old machines should be both double and tripple checked before we use them.
I have been thrown too many general refusals and judgements on vintage machines that turned out to not be ture. Some take the general point of view "they are old and worn and cannot be repaired properly", some machines have hardly seen use at all, and they where made to last and run for decades. Others say it's easier and better to buy a new machine, and the alternative they come up with is something very much inferioror to the vintage alternative. I don't trust general and random replies at all any more.